Why is my cat seizing, weak, has white gums, and won't eat or drink?

Oh dear! Seizing with white gums is a potentially life-threatening medical emergency. White gums indicate that either Toothless is severely anemic (low red blood cell count) or has very low blood pressure. Seizures can occur due to brain tumors, toxin exposure, epilepsy, among other issues. Walking in circles may be related to the seizure activity that she is experiencing as a post-seizure (post-ictal) phase of neurologic abnormality, or could be related to toxin exposure or other neurologic condition. Due to the severity of her clinical signs, it is not surprising that she is not eating or drinking. At this point, I strongly recommend taking Toothless to your nearest emergency veterinarian immediately for evaluation and diagnostic testing so that appropriate treatment can be started. I hope that all goes well.