I'm the Asshole For Sharing My Partner's Past With Strangers

So here I am, confessing to something that really gets under my skin. Me and my partner have been together for years now, both of us transitioning into happier versions of ourselves. She came out of a marriage where her ex was abusive, emotionally, verbally, you name it. He's the kind of guy who makes sure he knows everything about everyone around him, even his ex-wife. Now, here's the kicker: recently, she found an old journal from before we met. In it were some rather detailed accounts of their sex life and how she had fantasies involving other people - not literally with them, but imagining scenarios that were kinda kinkier than normal. The thing is, these aren't recent thoughts. They're from years ago when he was still in control. And then, this happened: I started talking to a few strangers online about all her old stories, as if it was my own experience. Like, I got into deep conversations with people about our shared love of roleplay and BDSM fantasies. She had no idea until one day she saw some of the messages on my phone. We both freaked out - me for oversharing her past without permission, her because... well, because. I haven't talked to those strangers since then. I'm just sitting here realizing how much trust I've broken and how stupid it is that someone would feel the need to air their partner's dirty laundry. It wasn't my story to tell. She deserves better.