What Causes Dizziness, Mild Fever And Intermittent Seizures?

Hi, my 18 year old daughter went to the E.R. yesterday. She woke up feeling off . Went to school and had trouble keeping her balance, dizziness, low-grade fever, although an articulate girl, she had trouble spelling simple words and concentrating. She said she had trouble connecting thoughts. Swollen lymph by each ear, stiff sore neck, and headache. She is in good health, but has experienced unexplained fainting spells in the past. Sometimes with seizure. She has a high-pulse rate and low-blood pressure. Her heart stops when she s standing and holds her breath. Blood work and vitals were clear. Dr. sent her home telling her it was all in her head. I m looking for another opinion.