I'm going to leave my girlfriend for getting an abortion
Are you sure you want to do that?
I saw some signs that she did it although I didn't want her to.
If she hid that much of a big secret from you then you should break up with her. She could be lying about other huge factors.
If a person is not honest, I can't be with them. She is not my property, but she at least should have been honest with me.
I can see that this was a difficult decision for you, but I really don't have anything else that I can say.  Maybe she just didn't want to hurt you, but the fact remains that she was dishonest.  If this is a deal-breaker for you, then you should be honest with her in return, and let her know that it can't go on.