How old is your daughter? Safety is most important, I’d give it to her straight out. I’m sure its difficult but sometimes you gotta do things the hard way. Good luck 
One little girl that was in my preschool was told her daddy is sick in the head and sick in the heart and that’s why she couldn’t see him anymore.
Use an analogy analogies are the best way to reach ppl that can’t relate or don’t understand or haven’t experienced a situation before especially children. include shot term and long term results adding as much color and detail in order to catch and hold their attention from beginning to end then ask her to explain what she learned back to you. Make sure not bash or insult the other parent our exes will do that by themselves by just being them.