wolf, it's not your fault! Maggots never crossed my mind until a while back when I read someone's post about them being on her injured rooster. It's just not something at the forefront of most people's "things to watch out for." You were focused on keeping her safe, happy, painfree, fed.......who would have reasonably considered this happening, unless they've dealt with it before? You are NOT a bad chicken daddy!!!!
I'd like to suggest a bath for her. Bathing a chicken is a little weird, but not hard to do. I had to do it for my barred rock when she got sick and had some really smelly loose stool all over her (sorry, but it's true - she really stunk).
Here's how you bathe a chicken:
1. Try to have 3 buckets that will comfortably hold your chicken for a bath. These could be muck buckets that they sell at the feed store or something similar. When we bathed my Dot, we only had one of those Rubbermaid totes with the snapping lid, but it was big enough and it worked. I say 3 buckets because there are 3 steps.
2. In the first bucket, you will want to put warm water, not HOT water. Chickens have a high body temperature, and you don't want to chill her with cold or lukewarm water. I'm pretty sure you don't have the chicken shampoo they use for show chickens, so if you have Ivory that will work. DO NOT use dish soap or any other soap that has a grease dissolving agent in it. It will make her feathers brittle and they will all break off.
3. The second tub needs plain, warm water. After bathing her in bucket #1, take her to bucket #2 and do as best as you can to rinse her.
4. Bucket #3 needs warm water and roughly 1 cup of white vinegar. The vinegar will ensure that all the soap residue will be washed out of the feathers. If not, the feathers can mat together, be sticky or become brittle and break. The vinegar rinse works perfectly.
5. Dry her in an old towel as best as you can. You will probably not get her completely dry. Feathers can hold a lot of moisture. My barred rock (who was 9 months when I did this) didn't dry for about 2 hours. You could use a hair dryer to dry her completely, but she may freak out. My suggestion would be to put a heat lamp over her or even just hold her and keep her warm as long as you can.
That's it! Perhaps a bath will flush out the rest of the maggots you're not seeing. Just keep a firm hand on her when bathing. She may want to fly out of the tub, but I have a feeling that with her injury she'll behave.
Feel better wolf - good luck!