Pinkie watched Rainbow shifting about for only about an hour before she went to sleep; she had observed Dash to the point of exhaustion.
She was awoken by loud, deep sobs.
Pinkie first thought the spell had expired. She reached a hoof over, and touched Dash on the shoulder. “I'm sorry, Dashie. I couldn't tell you the truth. You were just so happy like that.”
There wasn't a response other than tears. Her eyes were still closed.
She poked at her lightly, smiling weakly. “You okay, Dashie?”
No response.
Then she realised that she had never woken.
Immediately, she pulled the sheets down. The wings were still attached, and they still glowed. Dash was still crying.
Pinkie undid the straps as quickly as she could and pulled the thing off gently. Dash's cries abruptly stopped, and Pinkie hid the thing under the bed. “Dash! Are you alright?”
“Pinkie!” Rainbow tried to move her head. It looked like it hurt, but she didn't stop.
Pinkie reached over to push Dash onto her back. “Are you alright, Dash?”
“Pinkie, Pinkie!” Her voice was even more croaky than usual. She leaned over and tried to raise her forehooves to hug her. “You're still there. I'm so sorry. I'm so sorry.”
Pinkie reached over and brought her hooves over her own shoulders before hugging Dash tight. “What're you saying sorry for, you silly filly?”
“I left you. I dreamed that you got me some wings, and I—I left you. I just went. And then I flew around for a bit, and—” She collapsed into coughing, and Pinkie could feel some blood splatter down her back. She gently patted her on the back.
“—and then, I tried to go back to you but you weren't there and I kept looking for you and I called for you and I just looked for hours but I never woke up I'm so sorry I'm so sorry I'm so sorry.”
“It's alright. Just a dream. It's just a dream.” She pushed Dash so she could see her face. “I'll be there for you, alright? I won't ever go away.”
Dash shook her head. “But I will. I'm gonna just go and die and leave you here by yourself and just have fun in whatever happens next and I can't. I can't.”
She broke down into sobs. Pinkie patted her on the back.
“I can't. I'm sorry. I'm sorry.”
“It isn't your fault.”
“Don't you understand? I chose to go. I could've stayed with you and I chose to go. I'm disgusting. I'm a bad pony. I'm the Element of Loyalty, and I just went. I'm gonna just go and leave you here, and I'm so selfish that I'd wanna go.”
“You wanted to come back.”
Rainbow focused deep into Pinkie's eyes.
“And the next time?”
And Dash leaned into her barrel, and sobbed.
They held each other for a long time.