I was interested to be able to see what she was doing when she backed in hand. I stood at her shoulder, on the left side, took the right rein in my right hand over her neck, and had the left rein in my left hand. And I asked for a soft back. With minimal pressure, I got backing, and I got a head at or behind the vertical, but I didn't get softness. What I got was a relaxed poll and neck through the 2nd vertebra, but nothing else. Her jaw wasn't soft, and her neck behind the second vertebra to her withers wasn't soft - it was pretty braced. I could see one lateral muscle working very hard to maintain the brace. At some points her chin went almost to her chest. She also had a tendency to swing her hindquarters to the right, but that may have been because of where I was standing - she isn't used to backing in-hand - but it was easily corrected by my keeping her head straight with my right rein. I see that we're going to need to do a lot more of this until she offers up what I'm asking for, which is a somewhat more raised head, not behind the vertical, and where the whole neck and body are softening through the top line. Dawn's offering what I call "false softness" - it looks impressive but it's not the real deal. As I thought might be the case, she's essentially "locked" right through the area in front of her withers. It's no wonder she has overdeveloped muscles in front of her shoulders at the base of her neck. Once she figures out that it's less work and more comfortable to soften in the whole neck, I think things will resolve quickly.
To give her some relief, we did a little bit of lateral work, refreshing our turn on the forehand, which she did very well in both directions with very light pressure on her side with my hand.
We'll also be doing some lateral flexion work to loosen up her neck - I don't usually do a lot of this as it can lead to "rubber neck", but in her case her neck needs to be more relaxed and flexible, some rotational work so her face can tilt from side to side, more backing in the halter - I was beginning to get some good results with that and need to get that to transfer to the bridle - and some work with getting her to stretch her head down and in between her front legs - the stretching involved will be good for her. I'm also going to do some massage on her neck and shoulders to locate any knots and work on those. And then we'll be doing more backing in hand with the bridle - she'll have some moments of being frustrated and it may take some small "fits" and a while on each pass for her to begin to get the idea of what I want.
A horse whose head disappears to her chest, without full softness, isn't what I want. It may take some time to get there, but we'll take whatever time we need - we're in no hurry.