Unfortunately, one of those things that most agents would advise you to studiously avoid is opening with a dream sequence. I’ll try and explain why in my critique. First, the submission:

Title: Sorrowfish
Wordcount: 123,610
Genre: Fantasy
Language: US English
Synopsis: A half-trained music-mage summons Sara, a young sculptor from Kentucky, to Canard. The Song is dying but Sara carries the ability to save both worlds, if only she learns how to use it.
Text:
Sara’s vision rippled. In the corner, a tiny woman in a tall conical blue hat henpecked a young man. The tip of her hat wagged like a finger, admonishing him. Sara hovered a short distance away, a phantom. Is that really a garden gnome? This can’t be real.
To Sara’s left, a fire blazed. An iron stockpot swung in the enormous stone hearth. No stove, no fridge, no microwave. Terrible. Like camping all the time.
The pot boiled, releasing a pungent scent of flowers. Like the essential oils at the New Age shop. Flowers lay in neat rows on a scarred table, drying in the fire’s heat.
Sara ran her transparent finger along the table’s edge. Can I touch it? The corner had seen recent damage, darker varnish ripped away, exposing pale fibers. Sara traced these, drawn to the texture. She pricked her finger.
Great, I have a splinter. Why does this hurt so much if I’m just dreaming?
Sara focused on the young man. The air around him rippled. Like looking at fumes. Gasoline. I don’t smell any. She watched as a glowing spider’s web wrapped him. It faded, replaced by a transparent gargoyle. The creature flapped its wings, grimacing.
Whoa. I’m getting dizzy. Sara fixed her eyes on the young man’s face to steady herself. A shock of black hair fell into his eyes. He raked his hair back, his expression irritated, and those eyes fastened on her, ice blue.
He sees me.
“It’s begun,” he whispered. The flowers he held chimed softly, like real bells.
What’s begun?
The gnome nodded, her answer too muffled to hear.
Sara tried to ask what he meant, but the words wouldn’t come. She drifted. The room darkened, then all went black.
*

“so, you’re still sleepwalking, Sara.” Dr. Carol Sherman pushed her glasses up her nose and made a note. “Are you keeping a dream log?”
Sara nodded and winced as she searched her satchel. Her finger was sore where she had dug out that splinter. My dream. The table. She pushed the thought away. With a flourish, she handed her notebook to the therapist. Dr. Sherman flipped it open and scanned.
“Why did you want to have this session, Sara? What’s bothering you?”
Sara took a deep breath and let her questions spill out in a rush.
“Am I really just sleepwalking? Or is there any chance my dreams are real? It sounds crazy when I say it out loud, but that’s what I’m afraid of. I even got a splinter last night. How is that possible? I brought it with me so you could see. The dreams aren’t real, of course I know they can’t be…”
Sara wavered, pausing. Silence dropped like a cloak. She could only hear herself breathing. Her blood pounded in her ears. She focused on her breaths. I’m not crazy. A few irrational thoughts are normal. Exposing them, admitting them, is healthy. The doctor waited for her to continue, eyebrows raised.
Sara pulled a plastic baggie from her pack and handed it to Carol.
“You dreamed that you got a splinter and woke with one? Remarkable. But your mind created a story about the event. How did hurt yourself in the dream?”
“I touched a table in the gnome’s kitchen,“ said Sara. She leaned forward, putting her forehead in her hands. “I can’t even believe I just said that. I really am going nuts. Certifiable. Crazy artist? That’s me. Who dreams about gnomes? They’re not even really cute. They’re kinda creepy. Why can’t my crazy manifest with dreams about hot firemen?“
Ice blue eyes flashed in her memory, halting her tirade. She flushed and looked up at Dr Carol.
”Am I going to sleepwalk into traffic?”
Carol smiled. “Sara, stop trying to analyze what is real and what isn’t. You know you were only dreaming. You aren’t crazy. It’s ok to acknowledge that the dreams felt real but you also are firmly rooted in reality. That’s why you’re mocking the concept. You’re not seeing gnomes in your waking hours. Dreaming is healthy and normal.
“No, you’re likely not going to sleepwalk into traffic. You can get a splinter in your apartment, sleepwalking. That’s what happened. You processed it to become part of your dream.
“In dreams, we work through emotional pain. Your mind knows the level of stress you have even when you aren’t aware of pressure. Your subconscious forms dream images. It’s a perfectly normal experience after trauma. The accident, losing your twin sister, all of that is causing you enormous grief. Your mind translates a feeling of powerlessness to the experience of being a ghost. But you’re beginning heal and find your power. You touch something. That’s progress. But if you’re concerned about the sleepwalking, I can prescribe–”
Sara held up both hands, palms out. “No pills. We’ve been through this.”

Editorial critique: So this story starts with a dream sequence. Why is this widely considered a problem? Well, consider your reader. They know that your book is a fantasy, but they know nothing else about it (apart from perhaps what you put on the back cover as a blurb). In the first line you mention “a tiny woman in a tall conical blue hat.” Your reader has not yet identified this scene as a dream – there are no clues apart from “Sara’s vision rippled” and that’s quite vague. Perhaps she’s having an aneurism? Perhaps she’s drunk? We have no terms of reference to deduce that Sara is in fact dreaming. So your reader has to assimilate the fact that in this book, tiny women in conical blue hats exist. Since this blue hat-wearer appears in only the second line, we must deduce that she’s enormously important to the plot. So what is the tiny woman doing? She’s heckling some young man. Why, we wonder? What has the young man done? “Sarah hovered a short distance away, a phantom.” Okay. Now the reader is thinking, “Sarah has wings, or can levitate. Or perhaps this is some kind of astral projection? And why is she described as a phantom? Is she dead? That would explain the hovering.” So, dead Sara, haunting a village of tiny people who wear blue hats … “Is that really a garden gnome?” What? Is what a garden gnome? “This can’t be real.” At this point, perhaps, with this direct-to-the-reader statement (it should be in italics if it’s Sara’s real thoughts), we are beginning to get the message. It’s a dream. None of this is real. We don’t know if any of it is important, what to focus on, what’s going to be relevant to the story, and we don’t know if any of it is really happening. It sounds cruel, but we don’t really care, either, because we don’t know who Sara is. Imagine if a stranger sitting next to you in a diner started up a conversation with you. “I had this amazing dream last night…” You’d probably get the check, or make your excuses and move to a booth, hoping that “dreamer” wouldn’t follow you.
Things about dreams. They’re rarely that interesting, certainly far less interesting to a third party than they are to the person who experienced them. They rarely have any narrative continuity. They’re random images, or scenes, or snatches of conversation. Sometimes they’re just a pure emotion, of fear, or stress, distilled from something as insubstantial as a smell, or a closing door. None of these things make good writing. Writing should, unless you’re going to get all surrealist and stream-of-consciousness, have a narrative continuity, one thing should lead to another. It’s extremely difficult to describe an emotion in isolation in words.
With this dream sequence, we find nothing out about Sara for 290 words, or the whole first page, apart from the fact that she has a vivid imagination. The next 700 words are a rebuttal, by a person to whom we ascribe authority, of everything that she has just experienced. It was nothing. All a dream. It has no significance whatsoever. So we’re left at the end of your first thousand words back at square one. We don’t know anything. All we do know really, after your first four pages, is that Sara has quite vivid dreams on a regular basis. That’s not enough to draw us in.
There’s one interesting fact about Sara’s past that stands out in the conversation with her doctor, the fact that she lost her twin sister. Now go back to that person at the diner. Instead of “I had this amazing dream last night…”, they turn to you and, tears in their eyes, say, “I lost my twin sister in an awful accident.” Now what would your reaction be? I bet it wouldn’t be to move seats. I’ll bet you would say, “Oh my God – how awful,” and you’d be dying to ask (although you probably wouldn’t), “How did it happen?” This statement creates two reactions in you that the relating of a dream just doesn’t do. It creates emotion, that “OMG” empathetic shock, and it creates curiosity. These are the things you want to provoke in your readers at the start of your book, not, “Oh wow, what a vivid dream.”

So unfortunately it’s a rejection. I don’t think an agent would read past realizing this was a dream sequence. That would be a pity, because the conversation with the therapist is well-written and flows beautifully. I think you’re probably a much better writer than this dream sequence opening gives you credit for. I’d suggest having a rethink about where you want to start your book, whether dreams should be as integral to the plot as you seem to be making out, and how you link the two realities, the dream state and reality as we know it. Does Sara need to dream at all?