Poor Penny! Is she diabetic by any chance? Years ago I had a Lhasa that was diabetic and she suffered from seizures. The first couple of times it totally freaked me out, and she used to make the most ungodly cry/howl when she had one. It is fortunate that they don't remember them - poor babies. It's more frightening for us humans to watch helplessly, than it is for the dog to experience it.

Hope you can get Penny's under control for good - and soon!