Get her teachers and the school counselor involved. Part of the counselor’s job is to help socially-challenged students. Her teachers and the counselor need to be aware of how she’s feeling at school, and need to work to help her facilitate 1-2 friendships.
You are right that getting her involved in an activity she enjoys will help ease the impact of her social awkwardness. What about something like scouts that’s nearly free to participate in? Or start of join a weekly club in something she’s interested in. Similar interests really help to mitigate some of the social hurdles.
Another important piece is to work on improving her social skills and the actions that inhibit her relationships. You can work on emotional awareness and regulation with a program called The Zones of Regulation, right at home. And use some behavior modification to change her reaction to anger and frustration:
ADDitude Community Moderator, Author & Mentor on Parenting ADHD, Mom to teen w/ ADHD, LDs, and autism