Update - Day 17
I believe my hen has survived the fly strike. She's acting normal for her in her flock, and healing, etc. Attached are some pictures.
After Day 7, I started her on Penicillin G, 0.25cc per day for 5 days. She was noticeably peppier after two days of that treatment.
Around the same time, I started to add probiotic and electrolytes to the chicken's water, for a few weeks.
I sprayed the affected hen's wound with BluKote, twice.
I'm glad I did not decide to cull her. I hope this thread helps others save chickens from fly strike. My hen's situation was pretty bad, but I was able to save her. Sometimes you can!!!
Thanks for all your comments!
At Day 9:
At Day 10, with BluKote on wound:
At Day 17: