What Causes Redness In Eye Of A Child?

Hi my family of 4 it just getting over the stomach flu.we had it the last 2 days and today was the first day where we felt 100%. My 5 year old has still not bounced back. She is very lethargic, not eating much, says her stomach hurts and one of her eyes is blood shot but says it doesn t itch. It doesn t have any discharge either. Is this from the vomiting or do you think she may have pink eye? We ve been having her sip Gatorade and water all day but she still hasn t gotten back to herself yet.