Suggest Treatment For Persistent Dizziness And Fatigue

My 22 yr old daughter has been having dizziness, weakness, feeling like her head is in syrup. She sits down and after the spell passes she gets a terrible headache and becomes tired. My daughter had allergy testing 6/27. Out of 21 environmental allergies she was allergic to 20 of them. Since then she had dizziness only 7/2 & 7/3. She had spells 7/11, 14, 18 & 21. They last a couple minutes. She knows what is going on when these happen. She also has PCOS diagnosed 1 1/2 yrs ago. Since then anxiety attacks have started. She is also very sensitive to medications and has struggled with birth control to regulate her cycle. We have a neurology appointment in 3 weeks but until then she is afraid to leave the house. What could this be?