Hi My Daughter Has Fainted Three Times In The Past

Hi my daughter has fainted three times in the past 6 months. All while getting ready for school in her room. She would yell that she was dizzy and seeing sparkles. I was there for the first one. She was out about 10 seconds. The second time she fell on her carpet and woke yelling for me. Today she felt nauseous, sat on the bathroom floor sweating and as I sat with her she fainted and I held her. I thought she was having a seizure but there was no shaking, just her eyes rolled back. It freaked me out. What could be going on?