I have BC's, not that this matters here. It sounds like she might have had a seizure in the summer. I would take her in and have blood work done, and full Chem done. This will give you a clue to what is doing on.
One of my BC's started having seizures about 2 months ago. It turned out to be a low thyroid. A low thyroid will affect their brains as well as other organs. Your dog might be having liver issues now along with the low thyroid. Have them check both and make sure you tell your vet that your dog might have had a seizure this summer. They do not have to be full blown ones to be a seizure, they happen because the body is starving for some nutrients. I now have my dog on Natural Balance due to some of the added nutrition I have been told helps with the thyrod, and now giving him a vitamine each day. He is on thyroid medication and antiseizure meds for right now, and doing well. He is 7yrs.
I was having this type of problem with my yorkie and it was it his liver.
and she is only 6 years old