"Get over it" vs. work around it

Ok, where's the line? When do you decide to work around a horse's irrational fear of something versus making the horse work through it and desensitize?

Dixie and I have been plugging along doing pretty well. I didn't make it out to see her for three days this week - an eternity for me! - and she was HAPPY to see me yesterday. Whinneyed and ran to the gate. That made me smile a lot!

Here's our current problem. Fly season is warming up here, and I stopped on the way yesterday and bought a bottle of fly spray. I knew Dixie didn't like spray bottles - she dances around when I Showsheen her mane and tail - but I didn't know how terrified she is of fly spray.

I clipped her to the tie chain, got a brush, brushed her down, and got the fly spray. I thought she might not like it, so I had her touch the bottle with her nose for a treat a few times. She was a little wild-eyed but she cooperated. Then I pointed the bottle away from her and slowly squeezed the trigger and she flipped out. She surged to the end of the chain, pulled almost as hard as she could, and froze up in terror.

I'm not sure if this was a mistake, but here's the next thing I did. I told her to settle down and very slowly and deliberately sprayed her chest. She almost broke the halter, and she was as scared as I've seen her in a long time. I immediately backed down and waited for her to calm down. And waited. And waited.

Eventually, after I put the fly spray down behind me, I got her to relax and come take a frosted miniwheat from my hand. She refused to touch the bottle again, and if I was holding it she was near panic. Poor thing!

But the flies were buggin' her! I sprayed the brush, set the bottle down, carefully wiped the brush over a leg, and repeated. She was still on high alert, still not daring to move a muscle, but she let me do it.

So what do you think I should do now? Should I get a spray bottle of water and really work on desensitizing her, or should I just use a rag to apply fly spray?