My greyhound Shaianne had seizures from about April 2001 to Sept 2001 until the final one took her life. The vet and I believed she had epilepsy but after describing to the vets how she passed away we agreed that she probably had an aneursym that was pressing on her brain or a brain tumor or something similiar. There wasn't anything that I would have done differently as she lived out her final days fat and sassy and very much LOVED!
I hope your sister's dog is doing better Jo.