Stress, plus irregularity is normal in teens. She can go into the gyno and say she has irregular periods and they will put her on birth control if that is ever an issue.
Any ide why she still doesn,t have her period?
Semen can't pass through clothing unless it was very saturated with ejaculate. If you're honestly worried, just buy a pregnancy test. Its quick and easy.
There isn't any way she can get pregnant. I imagine you are a teenager, use protection so you don't knock her up. Please and thank you.