Arkady experienced a massive overdose when she was fifteen. It left her natural telepathy seemingly vulnerable to the changes in the timeline. She now seems to be able to see when a person will die. She also seems to be able to teleport from one place to another at whim.
She saves Luke from controlling the mind of his ex-girlfriend, an event that would have forced the other FreakAngels to kill him. It seems like she's taken it upon herself to change any futures she sees through her gift.
She has been mentioned as being the most powerful of the Freak Angels. This was later shown as being because she has died twice. Once Freak Angel "dies", they come back with stronger abilities.