What Could Delayed Periods Post Non Penetrative Sex Indicate?

Hi, I m a little concerned about my girlfriend. She is currently two weeks late on her period. However, she has been completely fine complaining of no symptoms. She has had an upset stomach the past 3 says but it has only lasted a few hours then gone away. The upsrt stomach had occured right after eating dinner. She has also been experiencing diarrhea these past 3 days only. Her period was suppose to come June 27. She is 17. We are both virgins. However we do take part in dry sex, where we have both been naked. However precum or sperm has come no where near her vagina as we are cautious about that scenairo. I ve been researching quite a bit and do not believe she is pregnant. What else could cause this? Thanks