No more fat sympathy. Have her re-apply to us with her new-found black fire in her heart. Public fat shaming is perfect in this case. Get the cheapest fucking one dollar cookie tray from Wal-Mart and the next time she tries shit, very loudly start shoving the cookies into her personal space while yelling about how fat and disgusting she is. The truth is that a 400 lb grease golem knows it's fat and doing this confidently will flip the bullying script. Hit them where it hurts.