Realising how much was swept under the carpet in my MLCer's FOO, I would encourage your daughter to let her Dad know how she feels.
Sometimes we have to speak, no matter what the response is. We do it for our own wellbeing and sanity.
As he his a man in crisis, it will barely hit the walls of his conscience, even if he says all of the right things in the moment. He may also get very defensive. Your daughter needs to be prepared for all eventualities. Our children can't control these MLCers any more than we can, and they need to understand that too for their own sanity.
Our boys were 12, 14 and 15 at BD, and their Dad has been a clinger, which has made things very tough. They have all told him how they felt (usually via email or text) a few times each. (mainly because he was trying to shove the OW into their lives constantly).
Yes, at first they naturally thought it would bring him home.
Their Dad promised them the earth - that the OW was on the way out, that she was moving to another country, and yes, they did break up for a few days until the OW fabricated a 'break in' at her house and had to move in with my MLCer so he could 'save' her.
The boys discussed their frustration at talking to the breeze with their counsellor, and with me.
Five years down the track, they have given up on him.
But I firmly believe that they did the right thing in speaking up.
They came to the conclusion that like an addict, unless their Dad was willing to make changes and get help, he was going to continue in the new life that he has chosen.
It breaks my heart, but I still believe it would have been worse if they were wondering if speaking up might have changed things, and they had always been too scared to do so.