This movie presented a character who wanted to do her own thing, but because of societal conventions was being forced into her 'traditional' role. The movie (among other things) explores this and ultimately gives her the freedom she (and apparently you) desired. It doesn't say that not being a tomboy is shameful, it was intended to show that being a tomboy was not shameful.

What's wrong with having a choice? Should all movies show men only doing manly things? Is it shameful for men to be in less than stereotyped roles? The presentation shown to many girls is precisely that they are expected to fall into certain roles. Breaking that mold is not a bad thing.