How do I get over my jealously of my girlfriend talking or seeing her family?

A little back story:
My girlfriend’s family has always disliked me from the get go. They have never given me the chance to show that I’m a good person. Her mother especially is the one who dislikes me. She is the type of mother that I don’t believe wants anyone dating her daughter because she wants her daughter to her self the rest of her life. So I am not allowed to go see her family with her who’s an hour and a half away. They don’t want any part of me. For some reason I get super jealous when she goes up to see them, or she talks to them over the phone or text. It’s almost like me and her mom are competing against each other for my girlfriend’s attention. How do I resolve the jealously issue within myself?? I’ve never been like this in any other relationship with the folks except this one. I’ve been with my girlfriend for 6 years now.