There is a slight and very confusing difference between "Insulin Resistance" and "Equine Metabolic Syndrome"
I am oh-so-fortunate to have one of each
As with Type II diabetes in humans, neither of these issues ever go away. They forever-after have to be handled by monitoring the diet --- a very strict diet that is low in starch.
There are many credible websites to read up on these diseases. Dr. Eleanor Kellon's site is probably the most popular. Equine Cushing's and Insulin Resistance Information
Keeping healthy hooves starts with what goes into the feed pan. Since your mare has already foundered, ditch the sweet feed and it really would be best to ditch all grains.
My 25 yo TWH, with EMS, actually has better hooves since he became EMS than he had his entire life, and he always did have strong hooves.
No alfalfa or any sort of legume hays.
Feed high quality, weed-free mixed grass hay.
Lastly, for the sad record, Arabs are on "The List" as being a breed predisposed to metabolic issues.
So are Tennessee Walkers. Two of my three TWH's are dealing with it but my 26+ Arab is sailing along without issue
Please don't take a ho-hum attitude. This stuff isn't going anywhere except to be a big burr under your saddle blanket for the rest of your mare's life
Ask a lot of questions. There are a lot of folks on this forum dealing with metabolic issues. We all have varying turnout and feed routines. That is because of that word "metabolic"; no two horses are the same.
What they all have in common is keeping their starch intake as low as possible, and either keeping a grazing muzzle on them for turnout or dry lotting them during the seasons the sugars spike in grass.