It sounds like your dog has had a seizure. She definately will need to see the vet. If she is doing fine you may be able to wait until Monday, but if she continues to have these episodes, I suggest getting her in to an ER this weekend. I know it is more expensive, but if the seizures continue, she needs intervention sooner than monday.
Seizures in older dogs can be caused by many different things-metabolic disorders like kidney and liver disease, low blood sugar, and also brain tumors. Your vet will have to run some tests to try to determine the cause.
Here is a website to read over:
http://www.marvistavet.com/html/seizure_disorder.html
It is possible this was not a seizure, but from what you are describing I am highly suspicious.
