Looks like she has a dry fungal infection of the frog. See how the middle cleft looks like a butt crack rather than a wide valley or dimple? That usually indicates an infection that can make a horse pretty sore, enough to not use the heels when landing...and she's a bit contracted, but that could be from the infection cuasing a toe first landing, which is what her barefeet looked like is going on. She's a little wry footed, (asymetrical) with that twist, and shoes can't fix that, neither could a trim, it's just her anatomy, but frequent trims can keep them more balanced. SHoes, as they grow out, can exacerbate it, rather than help.
I'm not going to get on my soapbox about shoes vs bare, just that I think the biggest problem your mare probably has is a thrush infection that needs treatment and some trimming to get her to land on her heels to stimulate that frog/heel area so it can decontract if it's able. You may find that the infection is the source of any all sensitivity, esp on rocky ground and sometimes even deep footing.
Her hooves aren't balanced, even after shod. Any time there is extra height on one side (you can see in the heel to toe angles that the heel height is uneven) compared to the sole level, then it's causing an imbalance in her coffin joint. Even if the horse toes in pretty bad, leaving extra heel on one side to make it straighter can lead to stress in the joint and arthritis. Some horses are better off with a visible defect, that allows even wear inside the joint capsules. The hoof should be trimmed to what the sole indicates, not what is pleasing to the eye when it's on the ground. The extra height can cause not only excess strain on the joints, but crush one heel, become underrun, or even a quarter crack and toe flare, depending on how the horse compensates.