I will go out and isolate her but I don't know what to do next. She's 3 years old. Any help would be appreciated.
Also what steps should I take to disinfect the coop and run. Overwhelmed.
If one has them, then most likely they all do.
Identifying what type of worm it is can be helpful in determining which wormer to use, hopefully the link I have provided will help to identify what you see, if not you can take a sample to your vet to have a fecal float performed to confirm identification.
These two seem to be the most effective for most types of worms, but again, I.D. would be best - Valbazen 1/2 ml orally and then repeated in 10 days for each chicken or Fenbendazole (Safeguard, Panacur) at 1/4 ml per pound for 5 days in a row.
Suggested egg withdrawal is 14days after last treatment. (Throw away eggs for 24days for Valbazen and 19days for Fenbendazole).
After worming provide some poultry vitamins and some probiotics/plain yogurt for a few days.
Identifying and treatment options:
Yes, you may want to clean her up.
Give her a good soak in a warm epsom salt solution. If her bum is poopy wash her with a little soapy water first (a drop or two of dish soap is fine). Then give her a soak in some epsom salt water.
Check her vent and surrounding tissue for any signs of wounds to make sure the worms your are seeing is actually internal parasites (cecal worms, round worms, etc.) and not maggots in a wound. Wash/flush the area really good. If you have her inside with the A/C going, dry her off well or you can use a hair dryer on low/cool to help dry the feathers a bit, you don't want her chilled.
I know it sounds disgusting and it can be. I haven't encountered worms yet, but dirty bum(s) I have. It just takes a little time, wear gloves and start working the soapy water into the vent feathers (a lot of it is fluff so it's not too bad). Once you get going, you will do just fine. Talk to your "patient" - she may talk back and you can have a conversation I've found that slow movement(s) and a calm soothing voice really helps. Have everything you think you may need ready. Extra water, towels, a wound ointment/spray if you encounter any wounds, gloves, etc. A helper is great if you have one, but you can do it just fine by yourself.
It crossed my mind when you mentioned they were all around her vent. Flystrike can happen fairly quickly especially in hot weather. So don't beat yourself up. You can do this
You can soak her in Epsom salts, salt water, betadine, or soap and water in a warm bath, Look for the maggots and get out any pus, you may need to use tweezers to get most of the maggots out. Repeat the bath again a couple of times a day until all maggots are gone, then dry it and apply plain antibiotic ointment (bacitracin, neosporin, etc.) Make sure that she is eating well with plenty of protein (scrambled/boiled egg, tuna, mackerel, meat) and drinking plenty of fluids.
Here's a helpful link:
Keep us posted on how she is doing.
You are doing the best you can. Try to get her to drink, dehydration can make her weaker. If she won't drink you can try dropping the fluids beside her beak. She probably won't take the first couple of drops, but I've found once the beak is moistened they will usually take in a bit. It's slow going and let her take her time. If you have poultry vitamins or electrolytes that would be good.
Please keep us updated.