Oh, Poor old girl! My opinion is that there is no coming back from that. Hopefully @casportpony will give you a second opinion. If she is no longer able to pass poop and her crop is backed up, I would say she only has a matter of a couple of days at the most, probably quite a bit less. Give her a nice blow dry with a hair drier (assuming she enjoys it) and keep her warm until you can make arrangements to end her suffering.
. Sadly regardless of whether it is caused by tumours or internal laying or salpingitis or Fatty Liver Haemorrhagic Syndrome or even plain heart failure, this lovely old girl is unlikely to recover from it.

