Please help, situation?

Well I have been dating this woman for a while. She is 6ft 7 and I'm 5ft 7. She isn't fat but she is slightly biger than average. So she asked me just recently if I wanted to come sleep at her house for a few days. Although she said that there is only one bed so I'm sleeping next to her. I have no problem sleeping next to her but I am sort of afraid that we'll if I'm sleeping next to her what if she rolls over on top of me and since she is so tall and slightly large if she rolls on me while she is asleep I can't well breath or it hurts and then I can't do anything about it cause I won't be able to move.