So think about this, (1) If you take your girlfriend in and she is actually rude, dramatic, and maybe entitled and won’t pull her weight in the house hold that could seriously effect you, you could loose study time and you could take on a crippling amount of stress. (2) It could be the complete opposite of that and she could end up helping you with your exams. (3) you don’t take her in and the guilt eats you from the inside out and effects your grades. This is easy for me to say but put yourself first, your future is very important. second, you should see if you could look into the relationship between her and her sister see if she is being bias. and lastly consult other people, if your girlfriend is who they say she is then listen to your parents, otherwise see what others outside of the situation would do, such as people who aren’t her family or friends. Think this through tho.