How do I handle my partner getting upset when I hang with friends?

So my girlfriend of 8 months gets weird every time I make plans with my friends. Like if I go to trivia night with the guys from my old job she’ll text me “guess you’d rather be with them than me” — which okay, not wrong but also not fair? Last weekend I went to my buddy’s birthday at the arcade bar and she didn’t talk to me for two days after. When I asked what was wrong she said “I just feel like you don’t prioritize us” but we see each other almost every day. I’m not doing anything shady — just laughing, playing cornhole, not texting her every five minutes. She says she trusts me but acts hurt & distant after every hangout. I love her but I can’t stop seeing my friends. My mom says it’s a control thing — my sister’s ex did similar stuff. But I don’t want to assume the worst. Am I being selfish for needing this? Or is this a red flag? It’s making me dread hanging out with people now which sucks because those friendships have been there way longer than this relationship. 🤦