Imagine looking for morality in a porn game.
It being okay or not is irrelevant, I'm not saying Linda is given a pass for it but her reasoning (except for the incest part) isn't that uncommon and not every woman who has kids fails to rebound, I've known plenty have and do. Some of it comes from the old popular "eating for two" myth that's 100% bullshit. Men don't have the babies wrecking their bodies excuse and at some point Bob changed and was no longer the person Linda fell in love with and that shit happens all. The. Time. Even without the change in appearance, Bob became complacent.