Hi Irischick, Not sure what to tell you. I did use the Witch Hazel in the soaking water and dabbed it on the vent with cotton balls; then dried her off and applied the Prep H while pushing the protrusion back into the vent. If you read online and some of the past posts on this site, you will also find that you can use honey (you stated you have an apiary) My girl prolapsed twice in a two month period. I really don't know what the time limit is. I am afraid that it can occur frequently in some chickens once it happens. If she is continuing to lay eggs while trying to heal, the straining process only exacerbates the condition. Also, pooping is a strain. I did read to feed them less.
Another piece of advice. If there is a way you can keep her close to the flock where they can see her, it will go easier on her when she goes back with them. When re-introducing her back into the flock, they tend to not be so nice.
Do read some more online and the past posts. They are probably more helpful than me. Good Luck! Raising chickens can be a challenge at times. We don't want them to be in pain or suffer.
Cheryl