My oldest son starting having febrile seizures shortly after turning 1 year. It is hereditary on my side of the family (my mom, me, and my sisters). They only occurred with fever. Did your niece have a fever? Any problems with her delivery? Epilepsy run in your family? I am sure she was taken to the hospital so the Dr has probably already ordered an EEG, spinal tap, and CT scan. I just said a prayer for your neice. God Bless.
Two of my children have seizures: epilepsy. The oldest one, age 12 has had days where she's had almost 100 a day. The youngest one always loses consciousness and most of the time stops breathing and needs CPR. Sometimes it helps to keep a diary for a few days to go back and track if anything occurs preceding the seizures. My kids have some predictable triggers and many more that are not predictable. I wish you blessings and if you have more questions, feel free to PM me.