Caught My Friend Masturbating

I was at a sleepover at my friends house (I'll call her Emma). We were laying on the floor watching TV with a cover over us. It was really late and I fell asleep. When I woke up I think Emma was masturbating. Her breathing was really heavy and I could see the cover moving between her legs in a rhythm.

At first I was freaked out but then it started to turn me on. I lay there without moving so Emma didn't know I was awake and watched her for ten minutes, until she finished. I think she had an orgasm because she made a little gasp at the end.

I have stayed round hers a few times since and try to pretend I'm asleep to see if I can see her again. No luck yet though.