Eeesh.. Spewing Venom like a cobra. Good for you for handling it with grace.
This is purely a question - but do mean exactly what you are saying about it being best for the kids if they live with you in the house?
As long as you aren't using that as a reason to keep her around and your motives are just that.. than so be it. She will think what she wants. As 25 said "It's life, it ain't always pretty".
Continue to feel bad for her. Staying empathetic is way better than getting angry.
M(f): 40 D'ed: 8/12
Show empathy when there's pain. Show grace when warranted. Kindness in the midst of anger. Faith in the face of fear.
