Afraid I don't know that product. From looking at the link you gave, I'd say it depends on the diet the horse is on, what else she gets, and whether she's prone to laminitis as to whether this is the right supp for her. I'd get a diet analysis done. Nutrition is not just about providing adequate levels of certain things, but it's also important that nutrients are all well balanced with eachother & not being overdosed either. Eg. Biotin is indeed one of the important ingredients for hoof health, but is also one that isn't likely to be in short supply if the horse has adequate green forage. Also, looking at the list of ingredients, it appears to have a high grain content that could be a problem for some horses, particularly lami prone or cushings types.
Diet is just as important as nutrition for hoof health. Eg. If you're feeding rich &/or large &/or infrequent meals of sugary/starchy stuff, if the horse is getting too little roughage, too much rich pasture, etc, this will also cause hoof probs.
Hoof care, trimming, shoeing, etc also have a huge bearing on the health of feet. On that note, you can send some hoof pics in, for us to give you more specific advice, and hoofrehab.com is one of many good sites that has heaps of info & will give you some guidelines for good management for hoof health & soundness.