What can i do to motivate my lazy, unintelligent spoiled daughter?

First, stop calling her unintelligent, that doesn't help the situation. Limit the things she is allowed to do. Don't buy junk food if you don't like her eating it, don't let her on the computer past a certain time, move it out of her room in fact, and don't let her have the car unless she's going to school and coming back. You are the parent.