Considering that Rhys explicitly used a continuation of Mor’s abuse and a destruction of her safe space without her permission for a political purpose, I’m not fucking surprised that she hasn’t come out to him. She probably can’t trust him not to trade the information to her abusers, just like he did with her love of Velaris (which, btw, included the only place she could be in community with other queer women, Rita’s). Because remember: it wasn’t that Keir wanted access to Velaris, or that he wanted to ally with Eris - or at least, that wouldn’t have been enough. He wanted Mor to suffer. That was why he agreed to Rhys’s deal. And Rhys knew that perfectly well.
And this is all canon.