Constant arguments

My girlfriend and I live together in a 3 bedroom apartment with my younger brother and his girlfriend. I feel like my girlfriend is often unreasonable and petty when it comes to communicating with everyone in the house. We're all living in a strange state and Corina (my girlfriend) is living away from her home town for the first time in 22 years. I understand that she feels lonely out here, and like she doesn't have many people to hang out with, but it's really seems like she refuses to get along with anyone here. She says that she tries, and don't get me wrong, my brother can be outrageously annoying(possible borderline bipolar syndrome) , and his girlfriend is often unwittingly passive aggressive and without couth. Although she is very outwardly nice, as is my brother most of the time. I am a very non confrontational person myself, but have recently been finding myself at the end of my fuse, performing rash and uninsightful actions that I haven't done since I was in my younger teens. I want to be this relationship to work. I've invested too much work and emotion into this to just give up. Please help me understand how to talk to and live with someone who seems to be getting the best of me.

Have you actually sat down with her and talked about how you and she are adjusting to life in the new apt? Dont be confrontational, but try to draw it out of her how she's feeling and you need to say how you are feeling too. It's hard to adjust to a new home and area so maybe some positive reinforcement would help her.

When my fiancé and I moved in together we argued a lot and almost broke up multiple times. It takes a while to settle down into a new pattern and it can be a very emotional time. It might even be worse because there are four adults living under the same roof. My fiancés brother moved in with us for a little bit and it almost cost my relationship with my partner. He's a fun and cool guy, he's a total ass to live with... Pretty much what I'm trying to say is its hard enough settling in with one person, I imagine it would be hell having to deal with three. Keep in mind your gf could be homesick. My opinion would be to talk to your gf about how she is feeling. Maybe you both need a place of your own, away from your brother and his gf? In my experience, communication is the best way to deal with things. I hope you work things out.