Thanks to a suggestion by carlaforpandas, this book will have a sequel! The basics of it are:

The potion sends Alex back home, but takes the thirteen vampires with her. In this world, they have to re-unlock their vampiric powers, and that requires Alex. They remember her, but she has no memory of them, other than their uncanny resemblance to the DBL characters. They have to go on a crazy adventure to both reclaim her love and restore their abilities. 

Still thinking of a title, but the sequel ending will be out shortly! Thanks again, carlaforpandas!