You can find a deep dive into the tropes and history of this series on its Tropedia page specific authors
While the term "Dream Girl" is a common song title used by artists like Kolohe Kai and the band Dreamgirl , in the context of Spells 'R' Us, it refers to specific story arcs where characters use magic to become their own or someone else's "ideal" woman.
Caleb stood there for a long moment. Then he pulled out his wallet.
The girl shrugged. “Fill out the form. Personality traits, voice preference, fatal flaw—gotta have a fatal flaw, it’s a union thing.”