Winnie - that must be frustrating. I'm not a parent, but I have watched parents do this to each other, and some of my friends have been on the receiving end of this type of thing.
She comes across, from what you've shared, as very insecure about her own parenting. Justifying and defending instead of just being happy with what is.
Maybe, as suggested, a few key phrases that can deflect her when she starts on the kids subject with you so that the rest of your friendship can remain intact? I think Mooselips is right, there is probably going to come a day when her life smacks her straight in the face and she will need you.
People like that I think need extra kindness and compassion. Seems ridiculous in a way, looking at their lives from the outside, but you never know what goes on inside someone. Doesn't give her carte-blanche to say or do whatever she wants however.
If certain behaviors are just not acceptable to us, they're just not and boundaries need to be drawn no matter why or what for our own sanity.
(((hugs)))