There didn't even have to be infidelity, abuse, neglect...
IMO, I believe some women feel like they can lose themselves with being a wife and mother. That becomes your identity, a dedicated wife and mother. At one time they felt more than that. Some women might, especially when children are older and not even having any ill will towards their husband, decide it's no longer enough for them. They want to live and dream again, put a plan in motion that they never thought they could. Many will think this is shameful. I think it's beautiful when it's that moment for them.
Another tragedy out of this, IMO, is if and when she's ever recovered (I think she will be) - the headline will be beautiful mom deceased. The core of who she was is lost forever.
Off my soap box.