An entity named Shadow camps out in her head and occasionally takes over, but Shadow also grants Jasper some powers. She is able to manipulate shadows to her will. This means she can use them to hide herself and others, she can teleport from shadow to shadow, and can make the shadows take a tangible form and, say, slam someone into a wall. When Shadow takes over, these powers are amplified and extremely strong.

Slytherin

She doesn't use labels to identify herself but you could say she is bisexual, she's had relationships with all sorts of people

She's kind of a hipster? Wears flannel and denim and skinny jeans with holes in them. Likes big sunglasses. Wears hats, usually like baseball caps. Likes wearing purple and blue and green. She kicks ass in heels. Usually wears Converse, but also has a few pairs of boots.

Control by Halsey
Who We Are by Imagine Dragons
(Almost any song by Imagine Dragons)
Heavydirtysoul by twenty one pilots
Heathens by twenty one pilots

Jasper definitely has some mental problems. Most likely has PTSD and depression. An evil entity lives in her head, for crying out loud. She was admitted to an asylum, in the mid-1950s, where she was treated horribly, as you might guess. The scars on her back often ache, and this is most often caused by Shadow when Shadow is angry or upset.