...So I guess, in answer to your original question, signs your horse's feet are hurting could include (but are not limited to):
-reluctance to move about on her own
-unusual stance, like leaning back away from forefeet or constantly shifting weight from one foot to the other, or pointing one foot more often than the other while standing.
-response to a farrier's foot tester
-"walking on eggshells" on very hard or rocky surfaces
-reluctance to pick up feet for cleaning, especially if a horse has already been trained to do this properly.
-shorter strides than normal
-changes in gait with a rider on vs. no rider
-abnormal changes in attitude, like "depression" or crankiness