Often times in the school cafeteria we would order cheese pizza, to stay halal, and next to it would the pepperoni (separated), and the cafeteria lady uses the same gloves to handle the cheese pizza as she uses to handle the pepperoni pizza, would eating the cheese pizza be consider halal even after knowing this?

In order to consider it najis you have to have certainty that it came in contact with a najis object, either the glove or the pepperoni or anything else.