What to do when your girlfriend's sister try to ruin our relationship?

girlfriend's (22) parents are conservative and they say she's still a student and it's not time to be in a relationship. But her sister hate this relationship for some other reason I don't know. Maybe she's just jealous. So they with her sister tell many reasons and gossips to her about me and try to destroy our relationship. She cry everyday cos of this. Every day her sister put forward our topic and get her scolded by her parents. My girlfriend is standing really strong and she won't leave me for sure.

Yeah I can understand a parents feelings and care for their daughter, but why the fuck if her asshole sister creating problems? Even she had a relationship during her college time. I'm soo angry at that fucking bitch and really wanna tell her to stop getting involved in our relationship. But this might create a bad impression. What can I do?

What to do when your girlfriend's sister try to ruin our relationship?
Post Opinion