Thanks HaWho. I think you're absolutely right. That comment about not liking anything in her life is what made me start thinking that this is a MLC. She's convinced herself that my son doesn't need her anymore, which is strange for a mother. She even started letting the cats stay out all night. (In the mountains, that's a big deal because of bears and wolves.) She told me that she doesn't really care what happens to them. She LOVES our animals...or at least she used to. They get the best most expensive food, herbal remedies for everything under the sun, etc. She's now willing to let them die.
I just wish that there was some way to make this clear to her (hence my post above about "accidentally" leaving an article about MLC affairs open on our shared iPad), but it sounds like I just need to let her figure it out on her own. I just hope she does before she hits the point of no return (gets married or pregnant). Ugh