Astrology

Mirra, Dipper and Mabel sat on the Mystery Shack roof, watching the night sky. The meteor shower they had been hoping for was mainly disappointing. They had only seen a couple shooting stars since they had camped out up on the roof.
"Hey, look, guys. There's Cassiopeia," Mirra said, pointing to an "M" shaped constellation.
"And there's the Big Dipper," Mabel said, playfully nudging Dipper with her elbow. Dipper pretended to ignore her. Mirra seemed to flinch a bit. It didn't seem to be because of Mabel.
"Dipper...your birthmark...," Mirra sighed.
"Wait, how did you know?" Dipper asked, surprised.
"I know a lot of things I shouldn't know," Mirra admitted. "It just feels weird for both of us to share names with things in the sky." She glanced down at her chest. Dipper couldn't tell why.
"What do you mean by sharing names?" Dipper asked. "I mean, I know I'm nicknamed after a constellation, but you?"
"Cetus," Mirra said. "There's a star in Cetus named Mira. It's pronounced the same. And since I'm a Capricorn, I basically represent two sea serpents."
"The poem." Dipper inferred. "That note we found. It said something about flying serpents.
You knew?"
"Yes. I just didn't want to say anything. Saying it out loud makes it more real." She started tracing the palm of her left hand.
"There's so much more..." She muttered. ""I wish my life made more sense."
"I wish Gravity Falls made more sense." Dipper teased.
"I just can't believe I'm here. I know, and it's horrible."
"What's horrible?"
*silence*
"It doesn't matter. If you knew, it wouldn't do anything except ruin your life."