In Rod Stewart's song, Maggie only does three things - she lures the poor lad, steals his heart, and (most memorably) she wakes up.  For purposes of this post, I'll assume we can take young Mr. Stewart at his word. 

It's only when she "wakes up" that she becomes the woman in Suzanne Vega's song and also grows up.  Good for her, but... 

The only question next is whether or not, now that she's awake, she's smart enough to stop and pay attention to her "book of dreams" from the time before became "tired of sleeping."  (Not trying to be cute here, believe it or not.) 

She's told us who she is not (i.e. "your Maggie May"), but who is she?

"The Lady of the House of Sleep is a familiar figure in fairy tale and myth...She is the paragon of all paragons of beauty, the reply to all desire...whatever in the world has been lured, whatever has seemed to promise joy, has been premonitory of her exitence - in the deep of sleep..."  Joseph Campbell (emphasis mine)

"Dr. Jones, Dr. Jones - wake up now!"  - Aqua