I don't see any evidence that she would have killed the children.
The 'motive' that CW gives, for her doing so, seems very unlikely. He says that he tells her at 4 am or so, that he wants a separation. And so she immediately goes to the girl's room and brutally strangles each one.
But SW had just taken her girls on a 6 week vacation, WITHOUT CW. And they had a wonderful time. SW has a very close supportive family, lots of close friends and team members, her own source of income, and was totally invested in her babies.
And if they separated, she was not going to 'lose' the kids. She had a fairly good chance of moving back to NC and having them much of the time with her and her family back home.
I see no reason that she would instantly resort to brutal violence, against her two precious baby girls, whom she doted on and lived for. It doesn't ring true for me at all.
SW was not the one that wanted to 'be free' from the responsibility of children and family life. That was all CW, IMO.