Seizures can be caused by sooo many things. Mold, eating rotten or really oily food, chemicals (including parasite preventatives), vaccinations, brain tumors, liver or kidney problems, shock, etc. Some dogs have them every day, some have them once a year. If her seizures are really that far apart, I wouldn't worry about it. Are you sure that's the only seizure she's had since last year? Some seizures don't involve muscle spasms or unconciousness at all. Sometimes a dog will lay there staring into space. Sometimes it will chase shadows or lights. Alot of dogs will snap at "imaginary flies." Some run around the house in a panic for no apparent reason.

I would make sure your house is free of mold, keep your garbage well away from Lady's reach, and stop annual vaccinations. I'd also switch to another parasite preventative if she's on one. Pills tend to be better than the stuff you apply, or have as a shot. And flea collars are the worst. Make sure she's not getting any really oily foods -- alot of foods, even ones that aren't really oily, can trigger a seizure. I'd keep her on her regular diet. I read somewhere that incense can cause seizures, though I'm not too sure about that. You could have your vet do a brain scan and liver/kidney tests just to rule out health problems.

All in all, if she isn't having them very often, it probably isn't serious and I wouldn't worry too much. Good luck!