My Girlfriend Was A Victim Of Drink Spiking And Rape

My girlfriend was a victim of drink spiking and rape when she went to a party in OCT 2014. In March 2015, she messages me that she is pregnant. I do trust her a lot and believe that she won't cheat on me. But my question is that, is it possible for a woman to get pregnant after almost 5 months of having an intercourse or has she been cheating on me? An answer would really help because I am not able to get to the right conclusion and feel only a gynaecologist can answer that question.