Girlfriend wants to break up, again!

So basically,
my girlfriend and I have been dating 6 months this week. We broke up once for 4 days around 3 months because she was afraid that she was bad for me. After that, we were closer than ever. I think that it's because her brother moved out at the time, and even her fathered agreed, that when he isn't there, she's herself. When he's there, she becomes her brother.

Anyway, so he moved back in about a month ago. Since then, we've had conflict. So she's been stressed out and we argue about stuff maybe once a week, and I think that contributed. A few days ago we talked and she basically said this:
-She never has doubts about ending it with us
-She's afraid that if we never get married that she'll never find anyone like me.
-Right before we talked, about an hour, she wanted to take a break.

So last night we got into another argument. Except this time, right after I got jumped. She was at a party 40 minutes away, and her ass hole friend thought that I was lying. So she comes down here and I cry on her about it and ask her to spend the night. She says "I don't think they'll let me.." and then says that her dad won't.

I get a text from her 40 minutes after she left, and she tells me that we should break up. I call her, and she no longer wants a break she wants to break up. After trying to persuade her that a break was better since she planned to get back with me one day, I exploded and said "A break up to me means me losing all feelings for you. Is that what you want? Okay, bye."

This morning I get a call and she comes over and gets her stuff. Guess who's there? Her friends and her brother.

Last night, she also told me "I've just been really stressed and I need to cut something off."

I'm guessing that something is me. It's just odd. Our good bye was 3 half hugs and no last kiss. So is this just temporary or is this serious?
My plan is to wait 4 days, and contact her when our 6 month was supposed to happen. Hang out, and take her somewhere cool.

Things she said last night:
-I'm no good for you
-We're disconnected (Even though we talk about our lives and spend a lot of time together)
-When I asked her if it was my fault, she said, "No.. it's nothing you did. I just think that it's both of us."

(I'm the first boyfriend she's dated this long, her first, and first person she's cared this much about outside of her family)

 

Saying things like, "it's not you, it's me" are signs that she doesn't want to see you anymore. Also, if she's moved out by now, then that's most likely a sure sign that she's done with you. However since you've broken up/gotten back together before, it's possible it may happen again. I like your idea about waiting 4 days and contacting her on your 6-month. That's a good idea.

 

She sounds really immature to be honest, I'm guessing you guys are quite young. I really get the feeling though that her brother may be influencing her in a bad way somehow..whether he is talking to her and trying to convince her to break up with you, or whether his presence in the house somehow makes her think/act differently towards you.

If you can get her alone somehow and away from that influence, I would try and talk to her and find out EXACTLY how she is feeling and why she feels that its best to break it off with you?

 

Try to get her away from those influences and see if things change. If not then let her make her own mistake and you move on. Once she sees how happy you are she will realize she made a mistake.