Like we've said though, it's not that she can't, it's that she etc.
Polissa doesn't seem to lack capacity in any serious way beyond being emotionally retarded. She's thick, but from what I've seen she certainly wouldn't qualify for a group home or a social/support worker (by Bongistan standards, at least, and we seem to have a marginally better social support system than the US, at least on the face of it).
She is thick, but not so thick she's actually incapable. She falls through the cracks, but mostly because she is in fact capable of running her life. She wouldn't actually starve if her family stopped feeding her. She COULD get a job, she COULD manage her ife, but she's mentally deconditioned to the point that she thinks she can't survive.
It would be no great loss if she didn't. I'm okay with people like her falling through the cracks, it means there's more money in the pot to support people who genuinely do lack the mental capacity to make decisions in their own best interests.