Can't really offer any explanation that would help you. I have known two epileptic dogs, and both took medication for it. I don't think that their owners felt that there was any one thing which triggered the fits though; they didn't seem linked. I do remember one of the owners felt that every time her dog had a fit, it took her a little longer to get over it than the last time.

I wanted to wish you and Jackie all the best. I hope she is more herself soon.