The white stringy thing is poop, though it's not good that it's white and stringy. How long has she been bloated. She's probably eggy if fasting and such doesn't help. I hope she doesn't become eggbound.
Females will occasionally fill up with eggs even without the presence of a male, just like most other female animals going into season. Normally they will either re absorb the eggs or they'll release them and eat them. An eggbound female cant do either, her eggs are sort of stuck. And she'll keep filling up until her eggsac bursts.