Maybe I'm just in the midst of a giant bout of positivity (highly unlikely) but I dont' see anything wrong with this at all. She's a teenage girl, this is her demographic. The cover is appropriately spring themed and the pictures are all tasteful and completely in line with both her image and the sort of country meets hippie chic bohemian nonsense that teens go nuts for. Flowers in the hair? Check. Long flowy nightgown dress? Check.
I'm not in love with Miley Cyrus but I see nothing inherently wrong with her getting the cover.