I'm sorry about your hen.
Sadly, internal/reproductive problems are very common in laying hens. Even with supportive care there's not a lot you can do but try to make them comfortable like you were doing.
Is she pooping? What's that look like?
There's often an underlying illness or condition that contributes to FlyStrike.
She may have some reproductive problems - Peritonitis, cancer or one of a few other conditions that laying hens are prone to have.
If the wound is healing, then treating it...