Katie Keel is the daughter of Richard and Dana Keel.
Katie is staying at her father's house for a while as per her parents' agreement. One night, she is kidnapped by a changeling and replaced with a fake. The fake Katie orders Richard to take it back to Dana's house, so it can secretly feed off of her. It also kills Richard.
The real Katie, along with an increasing number of other human children, are kept in cages in the basement of an abandoned house for the mother changeling to feed off of. Eventually, hunters Sam and Dean Winchester locate the children and kill the mother changeling. With her death, the fake children are killed as well.
Although not shown, Katie returns home to her mother.