Welcome to BYC. It looks like she was eggbound and has a prolapsed cloaca or vent. The egg has burst, and the string looks like egg membrane. The egg was probably shell-less or soft. It looks like the prolapsed tissue has gone back inside. If it comes back out, lubricate it and push it back inside and hold it there for a few minutes (disposable gloves are good here.) Hopefully, this is just a one time thing, and she will be fine. Once they prolpase it can happen again, if they strain to pass a large egg. If the red tissue comes back out and gets stuck, it may help to put some honey or Preparation H cream on it to help reduce swelling. But the main thing is to keep any red tissue moist with honey, oil, or hemorrhoid cream to prevent it from drying out, and to push it back inside as soon as possible.