Personally, if it's attitude, I'd pick up her foot and hold on. I would've thrown a Belgium doing that, except he got smart and just let me have his foot. Before you go to that extreme (and BTW, you need a 2nd person for that), when she lifts her foot really high, give her a minute to relax the leg. (My 7yrold always needs a few seconds before she puts her back feet where I want them for cleaning.) When she relaxes, then praise her, pat the bottom of her hoof and put it down.
And, yes, if you are nervous, she's going to know. Can anyone else besides the farrier pick up her back feet? Maybe you could watch what someone else is doing successfully with her and that would help YOU too.