What Causes Fever With Loss Of Orientation?

My friend has had a fever for a week now. Two days ago she suddenly became very talkative at work and stopped paying attention to other people. She began doing things that did not make sense (while cleaning, she kept going down 3 flights of stairs and coming back up with more mop water for the floor, even though we had already mopped!). While commuting home she became very angry and began yelling at a stranger for no reason. She is currently at home with her mother looking after her.