Your mare may be educated to your leg fine if you are riding two-handed. But she’s de facto not educated to your seat and leg if you can’t control the bend in her rib cage or move her haunches over with your reins in one hand and centered. Same thing for her neck bending (only) and too far in response to your opening hand.
These movements-- haunches in and half pass-- are tough to do within the Western scheme of things. JMO. That’s because you can’t use a direct rein to create any bend, or balance out leg and hand to get that bend from poll to tail. Of course you can do this when riding two-handed in a snaffle.
Also, IMO, getting a horse to be supple enough to hold the bend while not “falling” onto his inside front leg or simply turning in that direction (as in the haunches in) is a real test of just how broke to your leg and seat the horse is. In fact, I found myself wondering just today how much bend really good Western horsemen demand from their horses, given that it’s hard to make a bridle horse that broke to your seat and leg.
And the last bit of my opinion: In your spot, I’d back up, put on a snaffle and re-teach the horse that bend comes from my leg and seat. In effect, you start using hand and leg to get this done, gradually using your leg and seat first and your hand second as merely a reinforcement…. the way you’d use the spur to back up your leg if you didn’t get the response you wanted the first time. And I’m a big fan of teaching the horse to take his cue for the bend from what my seat bones are doing. That leaves the rest of my leg free to create other signals like “travel forward” or “travel sideways” or "maintain what you have, but pick up your rib cage between your shoulder blades.
I think good dressage trainers teach the shoulder in first, get the horse broke to the leg as an aid for “sideways”…. and then start by riding the shoulder in, adding their outside leg well back so as to then create the half-pass.
I’m not opposed to also teaching a horse a haunches in… slowly, like at the walk, riding two handed… as a prelude to teaching him to half-pass. To me, this involves me arranging my seat, shoulders and legs as I want when I expect a haunches in. I ask for that at the walk and wait for the horse to experiment with his body until he finds the “sweet spot” I created with my aids by moving his hind end over. To me, this is teaching him a signal for “move your haunches over.” I want a horse to have this tool-- a clear, obvious response to a distinct body position from me so that when I combine it with other things, or speed, he already has a clue what to do with his body.
Hope this helps.