Step 1 be sure there is no pain. And then...
What does this mare do when you run your hand down her back leg? When does the kicking start?
Treat her like a baby. Put your hand on her leg in front of the hock and hold. When she lifts let go right away *pat pat pat* and do something else. You've got plenty of time to work with her, no rush. Teach her to accept just lifting it without kicking. Then slowly work on holding it with your hand for a few seconds. Then ten seconds. We are talking days or even a couple of weeks. Literally, if she'll pick it up and set it down nicely without kicking that is good for the day.
One of my Thoroughbred mares did not know that she had a butt so picking up her back feet was traumatizing. She'd also had rough handling people do the 'back horse in corner and twitch nose' move one to many times so she would knock your block off for even looking at her back feet. The rope thing would have turned this mare aggressive on the handler SO I did the above. (First I made sure she realized that her butt is, oddly enough, actually attached to the rest of her and people can, shockingly, touch this whole hind end at any given moment) It took literally four months for her to accept a farrier AND to this day (1.5 years later) she prefers that her hind legs be kept very low when you trim. In her mind its that or nothing at all, take it or leave it ;)