My neighbor's filly managed to put a 2" cut in her nostril, stitching was unsuccessful, ripped open on day 3, just as the vet predicted. I used Nitrofurazone, generously, twice a day, healer without a scar and didn't seem to bother or sting/burn her upon application.
You'll have to gain her trust again, don't go only in with her for doctoring. Can you put on a neckstrap, so you can grab her easily without the hassle of haltering?
Good that some was stitched at least. The antibiotic should have been a depot shot, so she'll be good to go.
Poor girl. Both of you...