My gf had a weird period light blood brown blood brown discharge it never turned into a heavy flow could she pregnant or just weird period?

Hard to tell. It can be hard to tell if a woman is pregnant because some of the symptoms seen in early pregnancy can also happen in non-pregnant women. A urine pregnancy test gives a reliable result if done correctly. One can test about 3 weeks after sex (3 weeks after when conception might have occurred), or 1 week after a "weird" period. An Ob-Gyn doctor can evaluate any persistent or worrisome symptoms.