Originally Posted by SaddleStrings
Usually founder affects both feet. Maybe she has an abscess or a stone bruise? Or her feet could just be really tender? My gelding is prone to tender feet, so shoes are the best thing for him. Maybe have your farrier or vet re evaluate her feet.
If we're taking founder to mean mechanical changes, as different from laminitis as the initial inflammation/damage that likely caused it, I'd say laminitis effects all feet, but the backs tend to be healthier in form & balance, so less affected by founder, and as horses frequently have odd feet - one steeper than the other for eg, founder can definitely effect one foot much more than the others.
Pics would help, to give more than a guess of what's going on OP. Yes, shoeing can be an effective palliative to make the horse more comfortable, though I don't think they're generally the best option for the horse, esp with foundered feet & would lean towards boots when needed for protection. Yes, trimming 'too short' can definitely lame a horse, but I don't believe shoeing - assuming it's well done - is likely to have caused the lameness, just sounds like it hasn't helped it either.