Why did bloody Mary kill little girls?

bloodyMary or as reffered to as Mary worth' was supposed to kill people because her son was killed my somebody whom she couldn't find so shes searching for the killer to make them pay.

Nooo, that is not what happened at all. Catherine of Aragon is her mother and Henry VIII is her father. When she decided to go on a killing spree, and beheading anyone who isn't cathlic, she was murdered by Queen Elizabeth I, so Queen Elizibeth the II has some sort of relation to her death in a way.