Everybody is doing these so I thought why not?
-She has scars all over her body. It is still unknown where did she get them, she doesn't like to talk about it.
-She has whiteish-red sclera since she's almost always crying.
-She has dark circles under her eyes because she cries a lot and she doesn't sleep. She's always up until she collapses.
-She suffers from horrible headaches. She also hears voices that tell her to do horrible things, but she never obeys them.
-Her horn is broken due to an accident she had when she was a filly. She still can use magic (dark green in color), but to an extent. She also suffers from dizzy spells and headaches if she uses her magic too much.
-She has a scar she always covers with a bandage. It is always bleeding (it represents my traumas that come out when I'm depressed)
-She's always worrying about everything.
-She loathes children, specially babies. She hates when they cry or shout, and she hates that they seem to be scared whenever they see her.
-She has yellowish teeth because she never brushes them.
Sorry if it looks simple, but that's the best I could do.
EDIT: Changed the Wicked Shadow's student thing. I heard that we're not supposed to make backstories for our Sicksonas, so I will use her as a way of venting myself to make me feel better. So yeah, I will eventually think of more characters to add to my series.