One question I've never asked you: Do you think your WAW is cordial and friendly just because of her good nature, or do you think she may be aware of your NGS and use that to her advantage? My STBXW often tries to use my desire to "keep the peace" as a subtle form of leverage as we work out our split-up.
It's hard to know. I think it's a fair question to ask. My gut response would be that I don't think it's conscious or malicious, but I don't think it's zero, either. And further, I don't even know if I'd even blame her for it -- it's my issue.
The other factor here is that both she and I saw very, very ugly divorces between our respective parents, both sets of whom despised each other. We both have said how much we want to avoid that.