Any chance my girlfriend could be pregnant if she had what she thought was a normal 7 day period that was 3 weeks late and a neg test at 2weeks late?

Probably not, but...: If a woman has a regular normal period after sex, then she is not pregnant. If she cannot be certain that her bleeding was a normal period, then she could possibly be pregnant. A urine pregnancy test (available in stores everywhere) done 3 weeks after the last time she had sex will give the answer. If not married, settled down, and planning for kids, be sure to use excellent contraception.