A picture would help. That sounds like a prolapsed vent. It can occur with or without a stuck egg. Calcium deficiency, egg binding, and dehydration can be some of the causes. I also believe that some hens are just prone to it from a lack of muscle tone. The key is to lubricate the vent and push the red tissue back inside as soon as possible so that it does not dry out and die. Keeping the vent clean, applying honey, Preparation H ointment, or witch Hazel to the vent are some of the remedies. the vent prolapse may reoccur as soon as the tissue is pushed back in. Hold it there for several minutes (rubber glove suggested.) Daily warm epsom salt bathes may help. If you notice any dark tissue, that can be becoming necrotic or dead. Many of these hens recover, but many have to eventually be put down, especially if more tissue comes out. You will want to place her in a dark cage or room for 16 hours a day to stop her from laying eggs (if she is laying.) Here are some links to read:
http://www.the-chicken-chick.com/2012/04/prolapse-vent-causes-treatment-graphic.html
http://beautyofbirds.com/Prolapse.htm
