Over-grown hooves

I run 16 head and I have never had hoof problems on my cows until last year I noticed one of my cows hooves are starting to get too long. They aren't curling up or anything yet but I am worried she is going to go lame. I was able to get her hooves trimmed last June and I thought that would do it but they grew out again. Its just really weird because all my cows are out in the same pastures and they walk on rocky ground so they grind their hooves naturally except this one cow........I am trying to figure out why this is, maybe a hormone imbalance or nutrition thing? Should I just get her hooves trimmed every year? Could it be genetic? I own her mother and a few sisters and none of them have this problem.  Any suggestions would be greatly appreciated.
I will try to get a picture.

Hoof growth (just like hair or fingernail growth in people) can certainly vary from individual to individual in a group.  We have found it to have a genetic component for sure.  Some of our cattle never need to be trimmed but we have 1 that does need a trim twice a year....and now her daughters are the same.  In a big operation this could be reason enough to cull simply from the standpoint of preventing lameness.  We run a small operation so we can take the time to address trimming easily.  Having an experienced foot trimmer examine her feet and trim her properly can help.  You may need to keep her trimmed 1-2 times a year if you wish to keep her in your herd and keep her sound.