When a girl has what looks like a period, can she still be pregnant? my girlfriend had what looks like a period (4 days long, red blood, got heavier)

Yes: A woman isn't pregnant if she has a true period. Its physiologically impossible. The problem is that it is possible to have bleeding that looks like a period (but isn't) in early pregnancy. This bleeding can be confused with a period. Most of the time, if the bleeding is at the expected time and is normal in terms of duration and flow, its a real period. Best wishes!