My girl is a bitch how can i make her stop being one?

Omg I am so pissed my girl is just always a fucking self centered bitch all the time. Like when I'm pissed she don't even care. Like today for instance I called her in the morning right before she got up for work because I wanted to communicate with her and see what was on for the night and see if she wanted to hang out and plan some stuff. She says she didn't have time to talk at the moment and she would call me back right before she left for work. I just wanted two minutes of "hey you want to that tonight..or this? do you want to hang with me?" and she wouldn't give me that she never called me back before she left. This pissed me off a great deal because then I can't communicate with her till 3:30 and then she calls me after work for like a minute and then she said she had to talk to her mom and that she would call me back...a whole hour later she still hadn't called me so i called her and was pretty much like what the hell were you going to call me back? SHE WAS ON THE COMPUTER writing a paper. Why the hell wouldn't she call me back before that? like i know that shes probably stressed with homework and stuff but really my thinking is that if she really loved me she would call me back anyways and plan are night or tell me if she wants to hang out with me. I don't know she does a lot of things like this that just is heartless and mean. Anyway is there a way to make my girlfriend be considerate and stop being a bitch? I need some good advice