Our 2-month old miniature filly has a hoof problem...her heels are contracted and her hooves are very overgrown. We have had our farrier out, and he trimmed off as much as he dared, but since she is so little he says her hooves will bleed if he trims them to where they should be.
Your description suggests the farrier is less than confident in his ability to correctly trim the horse. Either the hooves are very overgrown and need to be properly trimmed, or they are not. Trimming a horses feet to "where they should be" does not cause bleeding. Maybe get a second opinion from someone more "daring" (experienced).
He says it is probably an issue with the muscles/tendons/ligaments in her legs not supporting her feet like they should be.
Could she be a dwarf mini? They often present considerable congenital limb deviations and are rarely correctable.
The only solution he can think to reccomend is limiting her pasture time, but I don't know how productive that would be.
Limit her pasture time to what end? Movement is relatively important in a young horse, regardless its size.
Has anyone heard of this issue before and/or have any ideas on how to fix it?
Without photos it is difficult to understand what the issue is, let alone how to fix it, presuming it can be fixed.
She is not lame and is otherwise very healthy and happy; she just walks on her heels and we worry about Navicular developing later in her life if it doesn't correct itself as she gets older.
Lot's of limb deviations do correct themselves in foals. You get about 6 months of usable opportunity to apply mechanical correction before the epiphyseal growth plates ossify and the deviations become permanent.
If the limb deviations are severe and become permanent, the longer term resultant articular arthritis, ringbone and sidebone will lesson your concerns about any potential navicular disease.
For more insight, photos and xrays would be helpful.