Update
Unfortunately, Pixie has had a setback. She had another seizure the night before last and with this one went totally lame as well. I thought the lameness was due to her arthritis but my vet said it's more indicative of a brain tumor, especially since she was seizure free for 7 years.
Our plan is to do some extensive bloodwork and start her on an anti-convulsant to control the seizures. We'll see if that's effective and then decide on a course of action.
Thanks for your prayers, everyone. Please keep them coming.