Girlfriends FARTS are ruining our relationship?

My 19 year old girlfriend has a problem farting while she is sleeping. The smell is so bad I leave the bedroom and sleep in the spare bedroom I would rather sleep in a outhouse.She does not do this while she is awake. While she lived at home I was told no one in the family could sleep in the same room with her. She has four sisters.I care for her but She is starting to turn me off.Any advice???