Non-PG13 (Strong Language): SO tired of my girlfriend's parents.

[Fabrication]

They abuse her and treat her like absolute shit. For no reason. If she does one thing, they're reaming her about it. But her younger and older brother NEVER seem to get one word from them if they do the same thing.

And the main thing I'm so pissed off about right now is that her dad decided to kick her out, told her to leave, then called the cops on her for leaving ALL BECAUSE SHE WASN'T FEELING WELL ENOUGH TO GO TO SOFTBALL.

[Eternal]

I doubt that her siblings never get in trouble like she does. How her parents react will differ depending on the situation, and since I'm guessing she told you this right after they got after her, she probably exaggerated about how much more she gets in trouble than her siblings do.
Are you sure she told you the whole story about her father kicking her out? It doesn't make sense that he would call the cops on her just because she wouldn't go to softball.
One thing you need to remember is that this is her parents, not yours so there isn't really much you can do but be there for her. In a few years she will be able to move out, so just help her cope until then.