My girlfriend confessed that she used sock accounts to test my loyalty. Has anyone else ever dealt with this?

The title speaks for itself but for context's sake, me and my girlfriend have been dating for over three years and even now, I still feel like I'm on cloud nine, every little thing I learn about her still makes me excited and I still feel like that awkward guy on our first date trying not to burst into flames when she called kissed me after it.

Of course, she isn't perfect, but I love everything about her and I just adore her in general. It's why this situation has rattled me as much as it has been for the past week now.

One night, I was over at her apartment for our typical movie night. We were watching that one documentary on a mom who harassed her daughter & said daughter's boyfriend online via fake accounts (this is important, stay with me) and when we got around to the part where the mom is y'know doing her shit, my girlfriend sort of laughed.

I chalked it up to that it was just the pure shock kind of laugh so I jokingly asked her what was funny. In probably the most casual voice I've ever heard, she said "nothing, just reminds me of the dumb stuff I used to pull with you."

Obviously, I asked her to clarify. She then went on this huge word dump about the fact during the first two years of our relationship, she'd make a bunch of fake accounts and then message me under these names trying to flirt with me as a loyalty test.

I remember getting these messages but chalked them up to bot accounts because of how crazy explicit these messages would get, going from stuff about strip-teasing to long rants on how good these fake girls were in bed. At the time, when I'd first tell these accounts that I wasn't interested/had a girlfriend, they would become verbally abusive, my girlfriend told me that it was a way to see "how I'd react under pressure" and she sort of added that she did it mostly when she was feeling insecure about our relationship and wanted to vent her frustrations out on me.

When I asked her why she would do any of that, she said it was because of her ex cheating on her with multiple girls all online and that she was just scared I'd be the same, she then said she doesn't feel that way anymore and moved on from the conversation after that.

It's been a week and I just feel lost on what to do.

My girlfriend has expressed that her ex made her feel insecure and that she's sorry if she ever acts irrationally, I told her that it was okay and if she felt any sort of way to just talk to me so I don't understand why this happened, I've reassured her about every single woman in my life, made sure to never cross any boundaries with women I'm or she's friends with, and of course, I've never cheated.

She told me that she doesn't do it anymore because she knows I'm 'tamed' and that she completely trusts me now. I feel a bit hurt that she felt she had to do some test on me in the first place but I also feel bad for feeling this way because I know she doesn't do it anymore and that she did it because of her dogshit ex. But again, I feel weird that she did some lab rat experiment on me at all.

Do couples usually do tests on eachother? Has anyone dealt with this sort of thing? I haven't dated for a while so I might be totally out of my element, appreciate any advice.