You want to go steady; she does not. What are you doing wrong? The answer is, probably nothing at all. Sometimes girls don't want to date seriously because they aren't ready for that type of commitment. They either aren't that interested in the first place or they want to wait until they are older to get serious. If you can talk with her about this issue, you will get a better feel for what her real reason is. Regardless of the reason, respect her answer.