I doubt you need to use a sand clearing product unless she actually ate a bunch of sand. We have clay soil and I asked my vet about psyllium and he said that the clay goes right through them and not to worry about it. It's because our type of soil is very clay-like.
Now if she was eating off a sandy surface, then yes, psyllium might be a good idea (although honestly I think there was a study to show that psyllium really didn't do anything. I believe it was in The Horse magazine).
One of my guys also licks the mud around ponds on trail rides and also eats dried moss when the water level is down. I don't know if he is lacking something or just likes the taste, but it freaks me out less than it used to. I figure if he likes it that well, there is probably something in it that his body craves. Who am I to say he's wrong?
Now I would still try to keep him from eating quantities of mud (and especially sand), but I figure a little lick or two or a mouthful of moss at a pond now and then won't kill him. And we can't be watching what they put in their mouths 24/7.