disclaimer: im not in any shape or form an expert, so dont take what i say as absolute.
there is one fundamental idea that i think you're not utilizing enough and is the cause of a majority of the 'flaws' i see.
you are writing in first person. It's incredibly personal. What you write is what the character sees and experiences. The words you use are what the character would use. When you desrcibe something, it is being described by the character.
1. complex vocab choices.
there are a bunch of these. they stick out and dont quite fit the sentence. this is supposed to be from the point of view of a reglular-ish girl. ex:
Licking my lip made me notice lacerations had started to dry and form scabs.
All I wanted to do was escape, but with my hands stained crimson, I knew it was over for me.
I wouldn’t allow her or anyone to benefit from me any longer.
The metallic taste of blood remained in my mouth, serving as a grim reminder of the damage I had suffered.
2. sentences: unclear/unnecessarily complex
I winced in response to a sudden ache that unexpectedly emerged, causing a sharp, stabbing pain in my head.
too many adjectives/adverbs. sentence became bloated. also you use stuff like "reason to", "made me", etc. to often. it's a crutch.
The metallic taste of blood remained in my mouth, serving as a grim reminder of the damage I had suffered.
grim reminder part doesn't really add anything.
The thought of fractured ribs crossed my mind, adding to the overwhelming sense of hopelessness.
you don't think of your fractured ribs. You feel them. the overall paragraph lacks the oomph of the situation. this doesn't reflect despair to me, more like detachment, which i don't think was youe intention.
3. lack of personalization
we're reading through the eyes of sylvia. these should be her thoughts. everything should be from her point of view.
She wasn’t wrong but failed to notice that I never wanted to.
weak impact. and it has to be about sylv not the sister. the 'wasn't wrong' part can be inferred by mc not denying this. Something like
"I never wanted this, any of this, but she doesn't care about that. It was always about her"
is personal and achieves a similar result while also conveying the mc's emotions.
The center of my world wasn't her as much as she wanted it to be.
same issue as above.
No one cared to stop me on my way up, either. They all avoided me even though I struggled to go down the hall. None batted an eye, seeing my clothes were stained red.
This is told from the eyes of a viewer. try to imagine how mc herself would experience this and describe it. Is she leaning on the wall as she walks? is she seeing straight? Maybe she's looking at people for help and they're avoiding her. maybe she sees pity in their eyes.
if you want to note blood on her clothes, make her notice it first. Maybe she trips or looks down and sees her bloody clothes. Maybe her hands leave red prints on the wall. Get what i mean? Direct and follow her line of sight
4. show and tell
there are a bunch of these but i am on phone and going for more examples is going to be painful, so here's just one.
“My date?! No! You fucking ruined my life! Not only did you take her, but now him too!” She snapped, appearing quite unhinged
this breaks immersion. dont tell me that she "looks unhinged". Describe it. Shouting, wide eyes, unstable breathing, etc etc