To me this is easier to solve on the line, than in the saddle. I personally would be WAY more worried ON her. On the ground you can go at her and MAKE HER THINK SHE IS GOING TO DIE immediately, and without question, for a brief period of time. Use whatever you have to go at her loudly and in a really big way. I would make her move her feet and keep them moving after the "die" part is over. Sounds to me like you have not really thought this was such an issue and have half heartedly dealt with it in the past. Inconsistency is NOT what is needed here. Every time those feet come up she needs to know, without question, that is NOT acceptable. No if, ands, or buts about it. Whether you are on her or not.
I would never, ever pull back on a horse who is trying to go up. Backing up is moving in the wrong direction. Turn her to disengage her and MOVE HER FORWARD.
I am NOT a trainer, but this is pretty common knowledge, at least I would think.