I am going to have to disagree with most of the others. It sounds like your girlfriend sees sex as a fun activity and does not see any reason to limit this fun activity. Strangely, a lot of people think that a woman denying herself some perfectly enjoyable exploration means that she is emotionally healthy. I have known women who slept with hundreds of men and ones who were virgins by choice into their twenties. The ones who chose to have little experience often seemed to have internalized slut shaming and had a lot of fear around being a bad, unlovable girl - the ones who did what they wanted often knew about slut shaming but choose to disregard it because they did not see why they should follow other people's opinions about what to do with their bodies. IMO that's a healthier attitude to have about yourself.

I do not see why her past experiences need to be seen as bad decisions at all. Perhaps there is the concern that she got her feelings hurt somehow? Doubtless she is emotionally present when having sex with you, and it's weird to think of her having that kind of sex with a bunch of other people. I'm guessing, though, that those experiences involved a lot more fun and games and less intensity of feeling.

Lastly, if you're worried about cheating, don't be. A person's sexual past does not make them any more or less likely to cheat when with you (unless their past involves being a cheater). She's with you because you satisfy her now.

You do seem to be aware of and fighting the double standard in yourself, so that's pretty cool. I hope it works out.