Jroxy is right. You have to know when you ovulate to know when you can get pregnant. Buying the ovulation prediction kids are a huge help for finding this out. Don't get frustrated. Although some women get preg right away, it is completely normal to take up to a year. Good luck!
It depends on how long her cycles are and when she ovulates. If she has no problems than keep trying. but try every other day around two weeks after her cycle starts. And get an ovualtion kit to test for ovulation. If you havent seen a doctor than see one to make sure everyhting is working right. Good luck!