There is apparently a this-Avalon tradition/injoke of clinking cupcakes like champagne glasses.

That is an adorable tradition and she will clink her cupcake as non-messily as possible. 

"No, you're supposed to do it hard enough that somebody loses some frosting, and then the person who gains frosting wins," explains Alec.

"Frosting jousting! Now that's a sport." She'll go at Alec's cupcake a bit more aggressively, then.

She loses. He licks her frosting off his cupcake triumphantly.

Having given tradition its due, the rest of her cupcake and its frosting is all hers.

And then most of them hug her goodbye, especially Brenda, who also wraps up Margaret's legs in snake section for some of the hug.

So much hug. She manages not to fall over while wrapped in snake section. "Goodbye everybody! If I'm ever back in town I'll make sure to stop by." She exchanges emails with everybody who wants to, and then she's out of excuses to stick around.

She can take the last cupcake with her; they were sold in a box of eight.

That's nice. She eats it in her room that night before flopping in bed as a dragon.

And three days later she gets on a plane to Seattle.

The flight is long and cramped and at least she and her parents are three people and can get a row together.

She resists the temptation to spend the flight thinking about bag designs, since she couldn't write her thoughts down; she reads a book about industrial robots instead.

Eventually they get there, and she unpacks her sadly Euclidean boxes. The only thing she didn't disenchant for the trip was Endurance Test Rock, which traveled inside several nested socks inside a box inside another box. She takes it out of the socks and checks on its luminosity.

It still glows.

What an excellent rock. Back to the normal desk-drawer hiding place with it.

The next thing she tries on the bag is "Replace the space inside this bag with a cubical space six inches on a side, leaving the external size, substance, and other properties of the bag unchanged."

She still gets a rigid bag.

 "Replace the space inside this bag with a cubical space six inches on a side, leaving the external size, substance, and other properties of the bag unchanged including leaving the fabric of the bag flexible."

Doesn't work.

Margaret is running out of ideas at this point. She might need to rework the diagram. But first, she can check out the Seattle Avalon and see if their library has anything on runecasting she hasn't already read several times. She knows where the entrance is from one of those critterlocked websites, and it's conveniently accessible by bus.

The Seattle Avalon has a rune dictionary, a book on historical runecasters (mini-biographies and accomplishments, no practical value), and a book of short stories in which the magic system is ostensibly runecasting.

There could be practical value in reading about other runecasters' accomplishments, since they'll at least help map out what's possible. She reads the biographies in little chunks in between cross-referencing the rune dictionary against the one she's already got to see if it has any new ones.

Accomplishments tend to be things like hiding and expanding Avalons, but some people are reputed to have other spells in their repertoire, including turning invisible or manipulating water.

The rune dictionary has some runes that don't overlap!

Turning invisible is cool but it's cooler as an item than as a one-off spell. Controlling water is also cool but she sees no reason to prioritize it. Are any of the people who worked on Avalons recent enough that someone who knew one of them might be findable?

New runes, nice. She will do lots of patient notetaking! 

Some of them might still be alive, given how old they were when they worked and the lifespans of their species and the lack of a death date present in this 1977 book.

Might be worth trying to track then down and pick their brains about space-folding, though any shop talk with an experienced runecaster carries some risk of revealing her as a dragon. She writes down the names of the potentially-living ones. 

If there's much of the day left when she's done integrating the rune dictionaries, she'll give the library their copy back and take a walk around the Avalon.

It's laid out differently from the one she's used to, but has many of the same elements - similar answers to the same question of how to be a small town full of people only some of whom can ever leave.