that's just how i felt the first time my daughter attempted suicide - like i failed my duty as a mother to protect her. it's a horrible feeling. i've come to realize, with time, that we can't protect them from everything. they need to learn how to take care of themselves when those awful 'others' show up occasionally.
your support for them, being there for them, teaching them how to turn away from abuse - all these things, including your feelings about what's going on speak to what a good mom you really are. the 'not good' moms wouldn't care. big hug.