Obsidian- I’m sorry for your friend and his sister, and glad you did all the stuff you should have done.
Can I suggest some nice things you and her brother can do for her now? Obviously, some of it might not apply, and I’m thinking of worst case scenario, but you can think about it.
Make sure she eats: she might be angry, depressed, tired, hyper or whatever else, but she’ll probably not be in shape to cook for herself or to remember to eat. That might mean bringing her casseroles, taking her out to dinner, doing a grocery shop for her or whatever, but do something, she needs her strength.
Bring over some nice bath stuff: she might not be concious of feeling dirty, but she may be taking a lot of baths and showers at the moment and she might appreciate it.
Make her feel safe: get a deadlock, peephole and chain fitted to her front door if she doesn’t have them already. If her building has an electronic entry code, ask for the code to be changed.
Make her feel accepted: if there was something she and her brother or she and you always used to do, keep doing it. Whether that’s a weekly poker and pizza night or just making fun of each other’s hairstyle and taste in music, whatever it is, don’t stop doing it. Something horrible happened to her and changed her, but not in the fundamental ways she think it might have-don’t let her forget that.
Don’t let her sit at home: get her out to the shops, the cinema, a restaurant, a cafe. Take her to safe, public, familiar places. Nowhere too crowded, nowhere too male (a sports stadium is not ideal) and nowhere where getting up and leaving would be a problem.
Thoughtful gifts: a comfy blanket to snuggle up in, a good book to distract, a CD of her favourite band, scented candles to make home feel more like home, you’re a girl, you know the drill!