Chihuahua's have more seizures than other breeds due to the anatomy inside of their dome-shaped heads. They commonly have hydrocephalus and other brain abnormalities.
In order to determine what is the cause of your dog's seizures an MRI would have to be performed. Sometimes skull X-Rays can show abnormalities.
MRI's are of course very expensive.
The leading causes of seizures in a two year old dog are abnormalities in the brain such as hydrocephalus, idiopathic epilepsy (unknown cause) and head trauma.
Other causes of seizures include: many infectious diseases including Lyme disease, endocrine disorders, hypoglycemia, toxins, parasites, cancers, and many more.
Some seizures can cause damage to the brain, hyperthermia (which can effect all organs of the body), can cause additional trauma, can cause cardiovascular abnormalities (abnormal heart function). If the seizure is due to an insulinoma, for example, the hypoglycemia that the insulinoma causes can be life threatening, if untreated.
Since your dog did not lost consciousness or seize, her epilepsy may not cause her any problems. However, you may have to monitor the number of seizures she has over a period of time, and if the seizures become very frequent you may have to seek veterinary medical attention for anti-seizure medications.
I'm not the Vet, but wanted to say that there is a thread going over in The Pet forum, under Dogs, that may have alot of your answers. It's on the first page titled: "Seizures....Epilepsy?" There are also web sights listed dealing with the subject (On this thread). Maybe this will help you....Good Luck...Karla