it's very good of you to care so much for her even when things can be bad between you two. because she is scared about being pregnant, make sure she kows you're there and interested in being there and knowing if she is pregnant or not.
when she takes the test, be there or tell her to let you know what the results are. then, if she isn't, relax and try to work out your other problems. if she is, then make sure she knows she's not alone by spending time with her. it will more then likely be on her mind 24/7... literally... so be there for her as much as you can... especially at first. then talk things over with her and make sure she knows you plan on being there throughout everything. the main things you have to do are be there and tell her that you will be there no matter what. if you keep up with this, she will feel a lot better i'm sure.