I would say this is not truly a run forward heel but a foot left without care for too long. I have a Navicular mare with a truly run forward heel that is near impossible to correct - even with filing it every 2 weeks and keeping the toe brought back.
Yeah, was speculating on why horse was put down, I don't know, just saw the pic online. It is obviously also very... ehem, overdue.
But yes, it is a 'truly' run forward foot too. My point in posting is that, IME, conventional peripheral loading shoeing does encourage this type of distortion, and then, without good understanding of hoof balance, they perpetuate the problem by shoeing to the foot they have... and so it goes, until hooves become grossly distorted like this. And unfortunately, in way too frequent cases, it seems that many farriers are simply none the wiser about it.
Re your 'navicular' horse, yeah, just good trimming often doesn't cut it with horses who have chronically crushed heels. They also need relief of pressure of those heel walls, by providing extra support under the frog/digital cushion **But not under the heel walls*. Of course, it's possible if this prob has been chronic since she was young & it's very long standing, that the damage may be 'too far gone' to heal, regardless. In which case, then palliative measures such as wedged shoes may be the best option for her.