You do know that the Depo- Provera shot is supposed to make your periods stop, don't you? I was on the DP shot before and from what I have read and learned about it, the shot has no effect on HCG levels in a woman. HCG is what is measured in pregnancy tests. You may want to make sure that your daughter took her shot. Also, you may want to retest her. Here is a direct quote from one site I visited:
A sensitive urine pregnancy test (home pregnancy test) is not inaccurate if a woman is using Depo-Provera or any hormonal contraceptive.