I believe diet- great nutrition- and lifestyle- lots of movement and turnout- can really improve the hooves. In the past I've used Farrier's Formula Double Strength and sometimes you can even see the growth line showing improved wall. Biotin is one of the major vitamins which is important in hoof growth. Just as in humans, biotin can improve nail growth and quality.
So I'd recommend the best quality feed and hay and 24/7 turnout, if possible and FF supplement. also important is having a good trimmer who really understands and implement healthy hoof balance.
So you wouldn't recommend putting her on a supplement?
Occasionally a supplement improves horn quality. Any improvement is good.
Will thin walls cause pain/lameness?
Not directly. But thin soles usually go along with thin walls. Horses with thin soles are prone to bruising. Horses with thin walls and soles usually require shoes all around to perform in athletic events. They also present a challenge to even the most skilled farriers. There is no margin for error in fitting and nailing shoes on a thin walled horse.
In my personal experience, Crossapol will strengthen hoof walls and soles so that shoes can be kept on, and shelly hooves don't chip off.
Crossapol has to be used as often as directed, and it does take about 3-5 months to see results. But it's worth the money as it worked perfectly on my horse. I used it for 2 yrs on the advice of my farrier. Now I can get by with just using durasole on the soles. but if needed, I'd go back to Crossapol as it worked for my horse.
My farrier recommended different supplements containing minerals, etc., that are essential to hoof growth and condition. I had the best results with Farriers' Formula double strength in smartpaks, but my Seminole feed contains the same minerals, just not in as concentrated a form.
However, what works for one horse may not work for another horse. Another boarder with an Arab had great success with Next level Hoof supplement, while it did nothing for either of my horses. It depends on the horse, his heredity/genes, his feed, etc. Consult with your farrier and vet to find out what works for your horse.
My horse is an easy keeper and consequently gets almost no commercial feed and is muzzled on grass. He has thin walls and soles. I supplement him with McCauleys BioTime and I'm very happy with the results.
That being said he's still shod on all 4 and needs to be. The biotin just makes it so the farrier has decent hoof to work with. He used to pull shoes pretty frequently and now he goes a full 5 week cycle and his shoes are still nice and tight.
It takes quite a bit of time to see results. I'd say minimally 6 months, possibly more. What I noticed first was faster growth. It still took close to a year to really see the difference.