Best friend or significant other?

So me and my best friend and my girlfriend used to be all best friends. Until me and my girlfriend got together then my other best friend and my girlfriend stopped being friends. And every time I hangout with my girlfriend my best friend gets all jealous and she acts like she hates me. She has told be before that she feels like a 3rd wheel do I try to hangout with her too. But whenever I hangout with my best friend I feel like my girlfriend feels like a 3rd wheel too. So it’s just rlly stressful cuz I love them both and don’t want to lose either one of them. Any tips? Lol😂