All the folks that have commented are accurate and this may be caused by seizures.
Seizures can be caused by trauma to the head, metabolic disorders (for example:portosystemic shunt, where blood bypasses the liver, and toxins normally eliminated as waste, travel to the brain, acting as a hallucinogen), and developmental disease such as hydrocephalis. The origin of the seizures can be central, located in the brain; or ideopathic (of unknown origin), or in the body: liver problems, metabolic disorders, etc; or can be secondary to exposure to toxins, or can be a side effect from a medication, a flea and tick preventative, or medicated shampoo as other examples. It is a very difficult problem to sort out.
This kind of behavior can also be caused by eye problems such as retinal deteroriation, other congentital diseases effecting the eye, parasites or toxins effecting the eye and more.
You should video tape some episodes so that you will be able to show your vet the behavior rather just to describe it since your dog may not have an episode during the exam.
A neurological and ophthalmology veterinary exam is important. The most common cause of seizures is ideopathic (of unknown cause). These and most other seizures can be controlled by medications or eliminating the inciting factor (if a toxin or flea and tick preventative, for example). Your dog will need blood tests, MRI, or CT scan, and others tests. Good luck and please keep us updated. Thanks
you definately should seek help from your vet. your dog could possibly be having seizure activity. take her to your local vet service to have a neurological evaluation, this might be expensive but its worth it. (:
You need to talk to your vet. She needs a neurological evaluation to see if there is anything physical causing the hallucinations or if she is having some seizure activity.