I am a Us citizen and my girlfriend might be pregnant. If she has the baby will it make her a citizen or what? I'm not sure about the laws or anything. I'm thinking she just might be using me or something. Any suggestions would be helpful.

No. She can not get any benefit by having a baby. Only the baby will be USC not the mother.
If you marry her and sponsor her then she can get legalized. Otherwise, she will have to wait for 21 years for the baby to sponsor her.
Good luck.