Oh dear...
Is she pooping at all? When you soaked her, did you happen to insert a finger about 1" into the vent to feel for an egg?
You mention that you do feel egg/mass in the abdomen? She does look quite thin, when was the last time she laid an egg? How long has she been in this "position" with her stance?
It's so very hard to know what to do in a situation like this. Give her a thorough going over - if she is pooping, then she is not "egg bound" (doesn't have an egg stuck). Feeling masses or an egg in the abdomen, to me, would indicate internal laying/reproductive issues - it could be cancer, tumors, Salpingitis or Egg Yolk Peritonitis (sometimes a combination). Without taking a look after she's gone, there's no way to know for sure.
It does sound like you have tried what you can, you can continue to offer supportive care over the course of a couple of days to see if she gets better, but she may decline further. If you feel like she is in pain/suffering, then it's best to put her out of her misery. If you do end her suffering, and aren't squeamish, you can do an informal necropsy yourself, looking for the masses/egg you felt in the abdomen and at her internal organs.
I'm very sorry, I wish I had better answers for you.