It is SOOO hard not to ask her to reconsider when I see her struggling with this, but I know that'll just make her dig her heels in more.
Yup. She doesn't feel like what she's doing is wrong, she still thinks it's the right thing to do. That doesn't mean it's easy, it's still a very emotional and difficult thing for her to go through. But she does NOT want the M right now and NOTHING you say will change that. So just keep doing what you're doing (validating). Very sorry you're going through this!