I think what LH19 is saying is that you don't have to be so polite. I've seen this with NGS, and how it seems to tear the guy apart if he can't fall back on his pattern of always being polite ........even to the one who is betraying him. I'm using the word polite instead of nice, b/c we see it show up in written text messages a lot. To a nice guy, it's unthinkable not to respond with politeness. (Politeness is what the nice guy calls it.) When they are told to practice not responding, especially to texts that ask no questions......... they just can't imagine doing such a thing!
Maybe try challenging yourself a bit, and just try it? Start with not responding to something she says that isn't a direct question. If you must answer a question, use less than six words. You'll quickly see how tough it is for you. It's not a matter of politeness, it's a matter of the NGS you have.
BTW, that stuff she said about you showing up for the kids, etc............is just fluff. It just keeps you emotionally engaged. For her, It's like buttering a turkey.
It is not about what you feel should work in your M. It is about doing the work that gets the right results. Do what works!