My gf is expected to have a period within 3 to 5 days, but she is not showing any symptoms of pms like she usually does 5 days before a period. is she going to have a late period? or is she pregnant?

Symptoms don't necessarily occur every menstrual period, and lack of symptoms does not imply pregnancy. If your girlfriend had unprotected intercourse, have her take a HPT a week after a missed period and you will have your answer.

PMS symptoms may or may not occur with every cycle. It can vary depending on a lot of other factors. The absence of symptoms with this cycle is not really indicative of pregnancy or a late cycle. You’ll just have to wait and see.