In my opinion, you're not ready for a serious relationship. Until you can get to the point where you don't have to snoop on someone, you're damaged goods and any relationship you have is going to end badly. Everybody deserves a little privacy and space and you owe it to someone you're with to respect that. Maybe you need some counseling to get over your trust issues.
As far as the foul, this is pretty small. She's likely just be venting. Yeah, her time at your family's house isn't the most favorite time for her, but she is putting on a good face for you so you can enjoy yourself while you are there. You need to give her the space to vent. Sure it is a pretense, but everyone puts them on, because no one gets to do exactly what they want every minute of their life. Eventually the pretenses put on during courtship fall to the wayside and she would let you in on the secret that your family wears on her a bit and you'll have to make some allowances for that. Or maybe she would come around to like them better down the road. It's called marriage and there are going to be some bumps in the road. This one is pretty minor.