Answer:
You might not want to do that because you haven't gotten permission from the girl, but if you think your relationship with that person is very strong and you rely on each other, just do it! Don't wake her up, that would just ruin everything. If she is very sensitive, wait until she rolls over, and if she's not, turn her around gently, slowly start, and just do it the normal way you do to a girl who is not sleeping. I like boys fondling mine, but I'm not sure if I'd like it while I'm sleeping. Don't go too hard on her and good luck!