My therapist said recently that I need to stop protecting my 18 year old child from their father's bad behaviors. That she is an adult and that she will need to realize who he is (she does) and be able to process that. That if I protect her from seeing that, she won't have the capabilities to deal with it later, but will learn those now while she is in therapy.
I was a little taken aback, but can see the wisdom there.