whiteline causing stringhalt?

I recently bought a 6 year old paint mare. I had ridden her and visited her both announced and unannounced 5 or 6 times prior to purchasing her. About 30 minutes after getting her off the trailer at our barn, I was walking her to her stall and I heard her stomp every other step. At first I thought she was kicking flies, but it was 10:30 at night. I had the barn manager watch her walk, and she was bringing her right hind leg almost up to her belly ever other or every two steps.

The trailer ride was uneventful as was the loading and unloading.

We called the vet out the next day and by the time the vet got there she wouldnt limp. The vet did flexion tests and we loged her in a walk, trot and canter, as well as turning her, bacing her, and doing whatever else we could think of to bring it out.

The vet did say she has a slight case of White Line Disease in that foot. and prescribed meds for it. She also told us if she starts hyperflexing again to take video.

A week ago I got a video of her doing it, only not as severely as before, and the barn manager took video of it the day before yesterday (that day it was just as severe as the first time) today I hand grazed her for about 45 minutes, and turned her out for 2 hours and there was no limp, only slight stiffness.

I am wondering if anyone has had a horse with white line exhibiting symptoms of stringhalt

sorry this is so long, I just want to be thorough