[Lain]

Stepping into the morgue, the siblings shuddered slightly. There was a slight chill in the air, which managed to seep into their suits and soak in as if they’d walked through a vertical puddle. As it was their first time in a morgue, they weren’t expecting the cool temperature of the room used to keep the corpses better in tact for autopsy. Or at least, that was the only assumption Nuru could come up with as to why it felt like it could snow in the room at any moment.

Kaylie turned to look around the room. There were a lot of lockers, each with a name written on paper attached to the door. The ceiling was textured with very specifically placed lights, shining over two autopsy beds. On one bed, there was nothing to be seen. It appeared akin to a metal desk, if only it had some drawers to make it look more so.

The other bed, closer to the two, had a woman upon it. She had black hair in a reverse bob cut. Her thin lips were closed fairly tight, her eyes left shut for the sake of not bothering the two investigators that had never seen a dead body before. Upon her body from the shoulders down was a white sheet, hiding from view the travesty the siblings were about to witness.

“Meet Emily Roberts, twenty-two. I recommend you both take a deep breath before I take the sheet off. A deep breath to brace yourself for what you’re about to see. It’s… Not something easy on the eyes, or the stomach.”

The siblings winced as the coroner began to pull the sheet off their potential victim. Covering her abdomen were slash wounds, deep enough to cut through her internal organs if the killer tried hard enough. “The gashes on her upper abdomen are so deep they punctured the heart,” Corona mused to Nuru and Kaylie. Nuru nodded before continuing his once over of the corpse. Her arms had scars of what looked like steadily, increasingly deep slashes or scrapes. When they saw her legs, it was identical- she had scars and slashes all over.

Nuru focused his sight on the girl’s hands. The fingers were coated in blood, especially the index, middle, and ring fingers. With a quick wiggle of his finger, he called the coroner and his sister closer. “If you look closely at the left ring finger, isn’t something missing?”

“There’s a lot of blood but… I see what you mean. The impression at the first knuckle, right?”

“It’s the right place for an engagement or wedding ring. I have a feeling this woman wasn’t alone in the world when she died.” Nuru sighed and glanced towards Corona. “Tell me, doctor, were there any DNA samples under her fingernails or in the wounds?”

“That’s what made us call you. There was DNA under her nails, but… It was all her own. It’s as if she’d been the one causing all these injuries. But it’s not Emily that had me call you here.”

t. English major, take what I say with a grain of salt because:
1. I'm a pretentious prick
2. I'm more concerned about style (never read much YA/teen fiction so I can't comment much on the content itself.)

First sentence is notoriously similar to what you might call a dangling participle. It's also generally a bad idea to use passive-voice sentence structure unless you have an explicit reason for using it (i.e. you don't know what commits the action.)
It's also not great to end a sentence with an adverb, just sounds kinda clunky, but again that's because most of my writing background is for professional and academic writing so those are things I try to stay away from. If that's your style, go for it.

The other bed, closer to the two[...]

This paragraph (or group of short sentences) has a lot of 'she/her' use. Perhaps introduce the woman first before describing? Or maybe use the coroner (dialogue) to describe her through a third-party rather than narration alone.

internal organs

Compared to the rest of your style, this sounds a lot more sciencey than the sensationalist/fantasy style you're aiming for (from what I can gather.) perhaps use the term 'innards'?

Otherwise, a little more gruesome than what I'd like to read (more of a slice-of-life/early-modern/postmodern kinda guy) but if that's what you're going for, it sounds fine.
Again, take my critiques with a grain of salt.