Okay, enough editing.  Thank you to the following people who helped me in the test audience:

These people read the whole thing and gave comments: Mommy, Fred, Ronni, Mike Lee, Reeny, Jessie, Laura, Victor, Cara, Meggie, Alicorn, Amanda, Rob, Patricia, Jeaux, Daddy, Stacy, Kim, Jeremy, Kalinda, Corinne, and Jay.  These people read part of it and gave comments: Jack, Deborah, Mikey, and Jessika.

My basic query letter (with personalized agent stuff at the beginning, and modified if needed):

Nobody understands the meaning of “a double life” better than Cassandra Howard.  A smart, sarcastic student by day, she becomes a different person at night; Dia, her charismatic second self, is the darling of a fantastical dreamland where she can do anything.  And while Cassie and Dia share their memories, they prefer to keep their lives separate.  That changes when they fall in love.

Mulligan, dreamland’s delicious drummer boy, sets his eyes on Dia.  But Cassie is pretty sick of her other self getting everything good about their life, and she talks Dia into helping her find the waking-world version of her boyfriend.  A mysterious portrait of Mulligan leads Cassie to two candidates: is it Terrell, the model who posed for the painting?  Or is it Jamie, the artist who painted it?  Maddening maybes play tug-of-war in her mind until she finds herself attracted to both guys, and she fears betraying her dream love if she picks the wrong one.

To test her contenders, Cassie begins to impersonate Dia in the waking world, but gets the shock of her life when her counterpart’s magical charisma and talent actually work in her favor.  When lines of identity start blurring beyond their comfort, they’ll have to uncover the nature of dreamland and deal with the repercussions of this love triangle.  (Or . . . love pentagon.  Whatever.)  And one thing’s for sure: dreams of happily ever after do sometimes turn out to be nightmares.