FWIW, the best method for desensitization -- which is what you're trying to accomplish with the broom -- is water. Tie her up and just hose her down. Concentrate on the legs since that's the issue, but feel free to give her a full-body bath too, complete with soap.
The biggest question here is one you have to decide yourself --whether or not the cow is being malicious, or just has an attitude problem. If it's just an attitude and she doesn't like the milker, "gentle" may work. If she's being malicious... well, over here I'd put her into the middle of next week, but that's JMO. I've been injured enough times I won't put up with a cow deliberately trying to hurt me.
Also, FYI, if she can still kick with the antikicking device that goes under the flank and over the back... then you haven't got it tight enough. Readjust it and try again... one on each side if necessary. If she's aggressively kicking the milker off over and over, then the 'kicker needs to be tight enough that if she lifts her leg she almost goes down.
The board-in-chute is a good idea in theory, but in reality, she'll probably get mad and get her feet up over the board... in the end she'll have skin scraped off her legs, might end up with some deep cuts, and you won't have her milked either.
Hobbles aren't too tough; the best design I've come up with is putting a rope with a steel ring around each leg (permanent) and then when it's time to milk, have a 6" or less piece of rope with a metal clip on each end (temporary)... takes less than 5 seconds to attach and keeps their feet where they're supposed to be. They'll freak out the first time, but after that you'd be surprised how well they mind their manners.
I've been in your shoes too, and I've oftentimes only had one mature cow of my own. One summer I had one cow, one calf, and milked the cow 2x/day by hand. Don't presume that the rest of us have huge herds. Also don't presume that because you have one cow and the rest of us have more than one, that your cow ought to be treated totally different. You have a
lactating cow. Your number one priority is to make sure that cow is milked out twice a day, because if you don't she's going to end up with mastitis and perhaps a dead quarter. You may have time to work with her, but when it's time to milk you don't have time to fool around with her idiocincracies. That milker needs to be on and off the cow in less than 10 minutes, and ideally 4-5 minutes. Putting that milker on over and over again for 20 minutes while she kicks it off and dances around like a spoiled calf is going to result in mastitis (has to do with the vaccum of the milking equipment -- run a search for milking times). Feel free to work with her however you like during the day, but when it comes time to milk, well, if you have to wrap her up in rope until she looks like a mummy so that she can't kick -- do it.
Looks like I've written a book now. :lol: Hope I didn't come across too harsh.
Best of luck with her.