@hoochinmama
First I'd make an appointment with a Neurologist. Since her insulin level is off I would make an appointment with Endocrinologist. Also perhaps see what a Gynocologist has to say. I believe that there are are Neurogynocologists who might have a unique perspective.
But you need and should demand answers from the so-called professionals you are paying. You daughter needs an EEG, MRI of the brain, and blood tests.
You mentioned a sleep study. are you sure it was a sleep study and not an EEG. If your daughter has seizures around the time of her cycle and a regular EEG was normal I'd ask for an Ambulatory EEG during the time of her cycle or if she always has seizures prior to or after the flow do it at that time.
As @alexm1994 mentioned a seizure diary would be beneficial.
Memory loss unfortunately is very common in Epilepsy patients. Both seizures and anticonvulsants can cause it.
When your daughter has a seizure does she fall to the ground and have convulsions.
If not can you share what happens during the seizure?
Take care,
Jake