Liver shunt or exercise induced collapse?

Hello Dr. Marie,
I have a 2 year old female lab named Harper. Harper loves to play catch with her ball and would run until she can not play any longer if we let her. She has an excited personality when it comes to exercise. Recently she had a strange episode after playing. I had thrown the ball about 15 times. I brought her inside. She was panting heavily which she always does after play. This time was different. After about 5 minutes of being inside I noticed her walking strange. She almost appeared to be staggering like she was drunk. She was dragging her left back leg for a few seconds and looked disoriented. I had her lay down. After a minute she got back up and started to walk around the dining room and living room slowly like she was lost. She also felt somewhat hot. I live in Wi and the temp outside was cool and in the 60's. After about 10 minutes of laying down she got up and seemed to recover from her ordeal. I called my vet and scheduled appointment the next day. I told her what had happened and she felt a few things could be possible such as a liver shunt or Exercised induced collapse. I reviewed both online and saw some videos that showed some activity that looked exactly like what Harper had experienced but more mild. I felt it was exercised induced collapse. My vet performed a chem panel and bile acid study. Today I received a call that Harpers chem panel and CBC were perfect. The bile acid study was not. Her pre-prandial was less than 1.0 umol/L. Her post-prandial was 55 umol/L. I was told she may have some sort of liver problem were it is not functioning at optimal levels and there is a possibility of a liver shunt or disorder. I am having a hard time accepting this. My dog is muscular,good weight, healthy, shiny soft coat, no signs of yellowing in the eyes or skin, pink/red gums, energetic, always eating regularly and so on. The only things odd that I have noticed is that her feces is a light brown, but I had switched her food to a lamb and rice diet with limited ingredients d/t her having some allergies. Prior to the food switch her feces were darker. This food is lighter in color also. She has always drank alot of water cause she plays alot. A hand full of times after playing this summer she would lay down immediately after playing and once and a while would look exhausted but this was with a lot of high activity play. This one episode is basically all I have along with a elevated bile acid to go on. My vet recommended a hepatic diet which I agreed to start today and we will check the bile acids in 1 month. I think I just need a second opinion on all of this. Do you think she really could have a liver shunt? Everything I read about it seems not to be her and also alot of sites say it is more likely a shunt if the post-prandial is over 100 umol/L. My gut is telling me she is healthy. Just curious on your thoughts.
Thank you for your time,
Alicia