Yeah, but that's her perception. The woman herself may see it entirely differently.
And if she and her ex behaved like adults the kids would be less likely to be badly affected for an extended period. Especially if 50:50 is working well.
The main thing is that OP is wearing rose tinted glasses over her little green eyes. She hasn't got clear view of this woman's life.
I find it quite sad that some posters are suggesting that it it inlikely that a break can go smoothly, that no woman, no child can be happy after a break up... and god forbid a woman moves on quickly!
As goblins said, it can be a matter of perspective. My life has a high and sunny ceiling, I find joy in lots of small things. STBEx PoisonousSIL however, has a very negative viewpoint, low cloudy ceiling. So despite all the good things she has (great job and colleagues, own home after break up that she instigated, lots of freinds and family support, active social life, new man in her life) she is so focussed on making BIL unhappy that she has hardly noticed that he needs no help in that department, rents a 1 bed flat, lost his job, drinks heavily, few friends, etc. She spends a lot of her time poking him, bemoaning her life with him. A life she got out of, a new life she is now refusing to live properly. She will die miserable!