Temper and frustration is common thing. That doesn't make it any better, though. Whenever you start feeling frustrated or angry with her, you should pause, take a few deep breaths, and ask yourself how -she- is perceiving what you are telling her. She might not understand if it's a new command, and if you are upset, that can make her upset and the situation will only get worse.
In this case, it seems she was nervous of the noises made by the men, and also nervous of the hose around her back legs. These things combined and made her scared, and when she fell, she must have been terrified.
Anyways, she will likely be nervous the next time, too. Perhaps you should start by desensitizing her to the hose around her back legs, before you ever turn the water on. When she can handle just the hose, (and keep in mind, she will probably take a few days, and will probably make you frustrated, so remember to breathe, and be patient, she's scared, after all) turn the water on low and just hose the floor or the walls around her. Let her see that it's not a big deal, she's not getting wet, yet, and everything is all right. After that, you can start moving up her legs. Go slow and if she starts to act nervous, wait till she calms down a bit and back the hose off of her. I don't know how long it will take, you might get this done in a day, you might get this done in a few weeks. You never know, with horses.
Also, keep an eye on her cuts and keep them clean. You might also want to make sure that she is up to date on her tetanus shots and everything.