Oops, I forgot to mention, that you should give her some calcium to help her pass the egg. Human calcium tablet with D3, such as generic Caltrate are fine, as are a Tums if you can get that into her. Crush the calcium tablet and feed with a small amount of scrambled egg. Give water. Try placing her on a moist towel on top of a heating pad set to LOW, and check to see that it doesn’t get too hot.
I would keep pushing the prolapse back in if you cannot see the egg. Once the crisis of the egg is over, keep her in a dark place or covered crate for 16 hours a day, then let her out to eat and drink for the remaining 8 hours of daylight a day. It can take 3 days to stop her from laying temporarily to allow her vent to heal. Once a hen has a prolpase, it can happen again in the future.