Of course! And yes, if her feathers are long you can trim them in the back if necessary. I have done the same thing and it helps it become less piled up.
I recommend adding 1 Tablespoon/gallon of apple cider vinegar to the water daily for the next week. Apple Cider Vinegar is very effective in chickens and humans and is a great probiotic. Also, add a small spoon of yogurt daily for the next week as a treat. This is all going to flush out the bad...
So this is vent gleet. Make sure you are using natural feed and scratch instead of harsh ones that can cause diarrhea and stick around to cause pasty butt and vent gleet. Since this has probably already become an infection sadly make sure to not use antibiotics. Antibiotics kill good and bad...