I made it.
When I called first thing in the morning, she said "Don't hurry to get me."
When we met up with her at the library, the first thing she said was "Can I stay two more nights?"
When I said that wasn't going to work, she wanted to know when the next time she could spend the night was.
It went very well. She went from a very attached (some have said too attached) child to a child who is still very much attached but confident enough (seemingly overnight) to do a sleepover with not a single glitch.
She seems determined to grow up.
*Many thanks to my sister for the sleepover pictures.