It seems like she focused so much on THAT moment that she didn't take into consideration just what it does to the rest of the story. Letting Slade die in the original version is revenge, it's taking back her freedom and self. Letting Slade die in Cain's version is... sociopathic. She let him die to what? Cover up her infidelity? I really don't know if she understands that THIS is what a lot of people were objecting to.
Comics can be a weird medium to step into writing. Marvel seems to be reaching out to grab writers from very diverse backgrounds. This is great but... when you have a ton of fans which encyclopedia-level of knowledge about the characters and the universe and writers who come into the project not knowing much, problems like this happen. I think this is one of those cases where editorial seriously dropped the ball. This is their job.