there is no perfect answer to these questions.. it sucks when a friend screws you over but this sort of thing happens all the time. Who knows.. she might end up liking you more in the end..especially if you keep it cool and you all chill together
1. Just talk to him. There's too much clout for there to be no weirdness. If you feel bad then talk to him. Be honest.. he was honest with you.
2. Don't contact her. It may be viewed weird by your friend and her. It will all work itself out in the end.