Worried about sister/names changed

My sister, Michelle*, has had a skin picking problem for many years. I'm not sure exactly how long but I noticed 6 years ago she had a problem with it. In the past she use to abuse adderrall and I think that's what got her started. She said she could see "things" in her skin magnified that no one else could see and she picked at her face until she had very deep wide wounds and sores. She also has a little acne on her face, arms, and back which I know she picks at. She may pick at other places I can't see. She does it while on the computer, eating, watching tv, in front of the mirror, in bed, basically anywhere. She is very reclusive, by that I don't mean she won't be around people but she spends most her time in her bedroom and won't come out unless its to eat. I also b elieve she may have an eating disoeder, she eats LOTS of food, and all unhealthy food. What I think is one meal she can eat 4 to 8 of in one sitting come back 45 minutes later and do it again. She also complains about her self body image and has low self esteem. As far as I can tell she doesn't still abuse adderall but she still picks incessintaly on her back, upper arms, shoulders, and the worst of it is her face. She likes to pick around her mouth and creates awful sores that she picks at so much its constantly red and oozy and scarred, they almost never heal. I love my sister and I think she is beautiful, when I ask her not to pick she says "I can't, I have to do it, I won't stop". I know this has had a huge impact on her self esteem and body image and she truly wishes she didn't. I plan to show her this sight but I don't want her to get mad. My dad is always working, he loves her very much though but doesn't know its a problem and our mom could care less but will insult her. She is in her mid twenties, how can I help her. Thank you all and best of luck.