There are a lot of information on seizure on here :-
http://www.canine-epilepsy.net/basics/basics_main.html
It is best to bring your dog to the vet. Call your vet and have her in right away. I wouldn't give her a bath right away. Just wipe her up and wait till she is much better. Have your vet check on her asap..it might be some kind of poisoning and you never know but a vet will.
I had a dog, Shih Tzu who had seizure. I couldn't remember how long it last but the after effect was his head is tilted to one side and it took him years to heal from that. The vet said there are lots of causes which is hard to identify but I think mine was either genetic or stress as he just came to us when he had his seizure. The vet said he might most probably have seizure again but mine never had for the next 8 years. I also changed his diet to human cooked food based on a balanced nutrition diet. I am not sure if that made him healthier but he certainly was.