I guess people in her family could do an intervention type thing as in, "If you don't lose weight, I'll never speak to you again", but that would only affect her mother. Peetz could move out but I highly doubt that would stop her anyway. If anything, it would probably speed up the eating/hoard. No one else gives a shit.
You make an interesting point.
For scientific reasons, it would be amazing if Peetz moved out.
Chintal's got to a point where she can no longer perform basic tasks and needs a moronic servant like Peetz to do them for her.
She can't put her own socks on, bring larger items into the luxury villa or even take out the trash. He probably also takes care of the litter boxes and helps with the insanely sexy leggings, who knows.
On a 'spiritual' level (pfff, like that exists in Chinny's reality), he's the only person she believes truly and unconditionally loves her for who she is, in all her disgusting glory. She kept him around for ego rubs when she was with Bibi (whether that 'relationship' was real is a different story) and she'd probably lose her shit if he abandoned her.
Peetz, on the other hand - as many have noted - doesn't care the tiniest bit about her. She's supposedly his best friend, but - in reality - she's just a prop he can fling his Twitter bullshit at.
She's said many times that she's impressed by his intelligence (proving her own stupidity and ignorance), so she's simply convenient to have around for his infantile SJW tantrums.
I think having Peetz around is the last stitch holding Chinny's world together. She can't and doesn't want to live on her own. If he left her, she'd fall to pieces in the blink of an eye and I'd pay good money to see that.
Edit: Last para