Ok so I've never had flystrike in a chook, but I deal with it regularly in sheep here in NZ.
She's looking good by the way

you did a nice job. Poor little lady is missing a whole bunch of skin from back there though ... I'd almost consider stitching it, but I could only tell if that was safe or appropriate by hands on inspection. It will heal just fine without it anyway, just take a little longer to fully cover over. But chickens have amazing healing abilities, I've seen one lose all but a thin strip of the skin off her neck to a rat and grow it back in just a couple of weeks. She'll be OK, you're doing great.
I'd suggest feeding her Comfrey if you can, I wouldn't apply it externally to a wound like that without again seeing it in person to determine of any deep damage is involved, as it can cause the surface to skin over too fast leaving an abscess, but feeding it to her will give her natural healing a safe boost from inside out.
For those that may see this thread at some future date ... The best thing I've found for flystrike is Tea Tree (Melaleuca alternifolia) essential oil, 1-2% mixed into any liquid vegetable oil as a carrier. I like to add 1% Clove bud oil as well, as it is a topical anesthetic ... it really helps with the pain.
Process is, trim away all feathers (or whatever else your patient has) from the area, making sure to clear at least an inch around the wound and any feathers that fall over the area too as these can harbor new eggs.
Gently brush away all visible maggots. Now liberally apply the oil you mixed to coat the wound. Expect some distress, as the oil coating will start to suffocate the maggots and they will all come swarming out at once!! The clove oil will kick in and numb the area soon. Again, brush away all maggots you see, and reapply the oil.
The tea tree oil is toxic to the fly larvae, so any that got missed or that hatch soon after will be killed when they contact it for the next couple of days. Also it is a repellent to flies, so no more eggs will be laid.
The tea tree oil encourages healing of the skin cells in the area. It is amazing to see the difference in a sheep treated with tea tree as opposed to any other remedy I've tried. Usually the short wool stubble in the area will all fall out over the next week, the skin is dead and has to regrow from scratch leaving bare pink scars for a while. When treated with tea tree the wool just regrows clean and white without a check. The skin is fine: no scar.
The tea tree and clove are both strongly antibacterial as well, so they work as a disinfectant for the wound. And of course the clove oil is a very strong local anesthetic, just try touching some to your tongue and it will go numb in a minute or so.
Normally in a sheep it is best to leave the area open to air, as closed bandaged areas on a sheep can turn steamy, rot the wool stubble and skin, yuck stagnant stinky damp bits, and encourage infection. However that is definitely not appropriate for a case like that pictured, as a chicken's rear is down there in the dirt, prone to being pecked by other birds, and besides the poor girl's abdomen is uncovered and so thin there ... that is her biggest danger right now, so fragile. The bandage you've done is exactly right.