Once try to obsrrve after she goes to bed. The first position how she lies, later. How she changes. If you keen on observing, you may b able to find out at what time after or how she changes her position. If it happens suddenly or without conciousness followed by noise in mouth, etc. Once she needs to see neuroligist (suspecting seizures
) n related check ups as precautionary action. If it all happens in normal pattern n with her consciousness&voluntarily,&responding well when you call, then you need not to worry. But it all depends on your observation.