She was exhausted the rest of the day. The next day she was her usual self. There are lot of different things that can cause seizures. Your dog should have a thorough veterinary exam including a complete blood profile to check its liver and kidney function. Only once ruling everything thing else out can you call it epilepsy.
Epilepsy basically is abnormal electrical currents in the brain which can cause a seizure.
When the dog is having a seizure don't panic. Make sure the dog is in an area where it can't fall down the stairs, off the couch or bed. Talk quietly to your dog during the seizure. Do not put anything in its mouth or pull the tongue. Just leave it alone, making sure it doesn't get injured.