Having a diagnosis and treatment is very important to controlling lupus or any other AI disease. There are many treatments other than cortocosteroids although they are often used because they are fast and effective. A second med will usually be introduced in order to taper off steroids. You should not ignore your daughters symptoms which seem to indicate lupus. Lupus can progress into something much more severe if left untreated.
Check out the resources under Learn about Lupus at the LFAI site.
If treatment is successful your daughter might see some or all of her symptoms disappear but no one can predict that. Not getting treatment is risking getting worse and lupus is a complicated and sometimes devastating disease.