Why do some women do things they wouldn't want their boyfriends doing?

So my girlfriend was allowing this guy to flirt with her for years and saying its not a big deal he flirts with everyone. He started texting her sexually stuff she said she's not flirting back so not a big deal and that I could truest her since she's not flirting back. We had a big fight about it then she ended up sending him nudes which broke me since my last ex girlfriend did the same thing to me.

I started having a lot of truest with her asked her to stop talking to him since it maybe me uncomfortable she refused said she won't do it agin and only did it since I asked for a break. We have kids together so I told her if it didn't stop I would find someone else to he with.. i givr her 3 warning for 4 weeks she kept talking to him, started borrowing money from him start smoking... so I slept with someone else.

She got very upset about it I did regret it a lot and told her for all I known she was sleeping with this guy. I ended up recovery all of her messages with him she wasn't sleeping with him but send him a few nudes dating months back and accept a decent amount of money from him.

Fast forwide our relationship gets better we started having a open relationship. I find a girl who super sweet which makes my girlfriend jealous that relationship ends since the new girl hates my girlfriend. I push my girlfriend to try dating other guys she gos on a few dates but all the men end up being creeps so we close our relationship. We argee to work on us agin then she out of no where starts dating a guy without telling me then I find out she's sending nudes out to her friend from 5 years ago. I lose my shit told her it all stops now or I'll block her out if my life.
Why do some women do things they wouldn't want their boyfriends doing?
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