AIO: for being upset that one friend revealed another friend’s gender transition history?

Three of us in this story: me, Charlie, and Sarah. All of us identify as women. We know each other from a hiking meetup. Charlie and Sarah have both been part of it for 5+ years. I joined last year. I’ve hung out with Charlie a few times outside of the meetup, and she and I have texted a lot - often late night kind of intimate details of our lives. She identifies with female pronouns, dates regardless of gender, and she and I are close enough that we’ve shared a lot of intimate details with one another (this is friendship, purely platonic), but never anything about gender identity, only that she mentioned that she often gets misgendered.

Sarah and I started hanging out more recently. She sends my gaydar alert screaming into the stratosphere (I may or may not admit to having a crush) but afaik she’s only ever dated men. She wouldn’t have any way to know I’m close with Charlie, and afaik Sarah and Charlie aren’t close and don’t hang out outside the meetup. I don’t know anything about why, or if they were close at not point.

Anyway I was hanging out with Sarah last night for maybe the third time, and she was talking about some of the changes in people she’d seen over the course of them being in the meetup. Like how one guy was way more mellow and kind, another had got better at not pushing themselves and was much happier / enjoying the group again. And then she got to Charlie. So it went like “Nick used to be xyz, Robert use to be abc…Charlie used to be a boy.”

I didn’t say anything in the moment. I was frozen. Sarah had just outed Charlie’s gender transition history. I didn’t know it before she shared it with me. Also I’m aware I don’t know any details now, just that Charlie has gone through some form of gender transition. To be clear: I do not care. I just don’t think it’s my info to know unless Charlie were to share it with me directly. It’s also possible that Charlie doesn’t care that Sarah shared this. I doubt it though, bc this transition was something she talked openly about, we have the kind of friendship where I think she would’ve mentioned it by now. (We’ve had in depth conversations about biological issues of peeing standing up with female anatomy. We are close, and not a lot gets held back - but she held back this, and I respect that it means it’s likely deeply personal).

So the main question is: AIO for being upset that Sarah outed Charlie, without knowing any more information about Charlie’s comfort level and openness about this?

And if you’re feeling helpful, feel free to take a step further with your thoughts on WDID. I don’t want to make this a bigger deal than it is… and idk if it means saying something to Charlie, saying something to Sarah, or saying nothing at all.