A lot of girls dont realize that when guys get upset about their gf telling them their dating history its not reslly cause they were with someone else. Like obviously everyone would prefer their partner to have zero history but thats a pretty unrealistic demand.
What upsets guys is when girls talk about it like they miss it, or they preferred it to what they have now, or dont regret a bad event. Like if a girl said "oh i went there once when i was dating [x] and the food and music was good, we should go", thats totally okay, no bad thoughts. But if a girl said "oh me and my ex would drive out there to have sex when his parents were home", that would kill a guy. Girls just dont have a relationship filter and dont understand we dont need to hear literally everything about them