Barb is crazy and senile, but she's not entirely stupid. I think that Barb's main deal now is that she knows that she's alone with no family and friends (aside from Chris) and that her life is drawing to an end, and she just doesn't give a fuck. She doesn't have energy to do much more than sit on the couch all day. If bill collectors call, so what? She can just hang up on them. Someone tries to evict her? So call the cops and have them drag her out and all her stuff. (not an easy task) If Barb wants a new car, new TV, or whatever, she's just going to buy it if she can. She'll enjoy it the last few years of her life as much she can, guarding her horde, and she doesn't give a fuck what she leaves behind after she passes away. If the repo man comes by, or if she leaves Chris with a stack of unpaid bills, so be it.
I really think that's where Barb's at right now, as far as mindset goes, at least.