Well, if she thinks she's pregnant and it's past when she has a normal period then she can take a pregnancy test to find out for sure. But usually, if you have a period, you're not pregnant.
Bleeding after sex can be normal
if they didn't use a lot of lubrication and didn't take things easy-- especially on the first time. If she's still bleeding then she needs to speak with a doctor.
If she hasn't had a pelvic exam or anything then now is a good time to get one-- then she can check for infections and ask about any complications during sex, especially if she's still bleeding. Birth control sounds like a good idea, it's a lot less stressful that way.