Spray her legs lightly with the hose first. She'll probably dance around and act like she hates it, but once she realizes it feels good, she'll stop. When she stands still, praise her abundantly. Move the water up to her body and avoid her face at first. She'll probably dance around a lot, but when she stops, praise her and take the water off of her. Soon enough, she'll stand for you.
As for fly spray... she'll get used to it. It's usually the sound they don't like. I desensitize mine by rubbing the bottle on them - butt, back, neck - and when they seem to relax, spray their legs first. Eventually, they just get over it when they realize it's an irrational fear - it isn't going to hurt them.