.I had unprotected sex with my girlfriend on the 7th day from day one of her regular 28day cycle but did not ejaculate in her.My question is what are the possibilities of her becoming pregnant?

ANY time there is penile insertion there is the risk of pregnancy. The risks can be reduced but not eliminated. There is no way to predict the possibility of fertilization.

You have to wait to see if she misses her period.

Thank you much.how reliable is the !4th day mark for ovulation though?

Depends on the woman.