Um, even sharing it with her sisters still crosses so many boundaries. Would you really be ok with her sharing it with them? Anyway, sharing it with the guy is cheating and her excuse is nonsense. Why not send a video that’s not one of you guys in the bedroom? Why a sex video to show how happy you are? If my partner and I had an agreement where we both agreed it was ok to send those out that’s one thing, but if it’s a bone of contention and he did it, well, it’s a breaking point for me. It’s a violation of my trust. You have every right to be upset.
Leave her. The kids will be fine with the two home balance the courts will setup.
First off, this is totally illegal and a disgusting thing to do (on her part with sending it) and it’s a total breach of consent. Second, this is so messed up and not okay in any way. She’s just gaslighting you now.