When I had to put Desitine on my horse's nose because of sun-burns he's also fight me for it. Horseman's Dream does have an odor (a pleasant odor I think
) but to a horse it could be extremely strong smelling.
I know my horse didn't like the feel of the stuff on his nose, so that's why he was fighting back.
Are you holding her with her halter on? If not I suggest it. Though she may not like it, it is for her better good. Have a friend or family member hold some treats and while you put it on her have them give her treats...so she associates that with something good.
Also, on a side note, depending on what part of the country your at, flies really like it and so do other typse of bugs. So if you are at a buggy part of the year, covering it up with SWAT will also help heal it.