No, for a couple of reasons. Having a period at any point after sex, is a signal that the woman is not pregnant. Pregnant women don't have periods. Some pregnant women have a bit of bleeding at the time when their period would have come if they hadn't been pregnant, but it would be lighter and shorter, if she had any bleeding at all. Most women don't have "pregnancy bleeding" at all.
Second reason is, if the sex was only two days before the period, she would not have been ovulating at that time. Unlike men, who can produce sperm any time of the month, women only pop out an egg once a month, two weeks before the next period. It is not viable after 24-36 hours. So, if your girlfriend's period came only 2 days after unprotected sex, there would have been no egg available to fertlize when you had sex.
If you are nervous that she is pregnant, ask her to take a home pregnancy test. If it has been more than 14 days since the sex, it should be accurate.