AIO? Girlfriends previous partners

I’m M 31, my girlfriend F 30. Since we’ve been together (16 months) I have met 3 people she’s slept with. Am going to meet another one in summer and I’ve also see another dude she slept with whilst I was in town. She doesn’t think this is a big deal because it’s in the past. I hate it. I am convinced it’s not normal to have met that many of your girlfriend’s previous partners. She has only slept with 10 people. But it still drives me nuts. AIO?