Hmmm

People addicted to stimulants often exhibit such compulsive monotonous behaviors. Maybe when she was all amped up on speed, she sometimes bored of packing words into that lengthy Atlas speech, so she turned her drug-charged attention onto something else: sorting and packing stones.

What SydB said. Meth users are notorious for compulsively collecting and sorting objects.

Arnold's theory is more likely. Apparently, she was a stamp collector as a child, philatelia being a (humorous) marker for Asperger's.

Asperger's is frequently confused with ADD. Speed tends to help people with these issues to focus. It could be that people who tend to order things also self-medicate. Hence, the association between speed use and collecting/ordering may be correlation, not causation.

Kling has a good theory...

It's rarer for females to be diagnosed, but my six yr old daughter was diagnosed with Asperger's syndrome a couple of yrs ago. She is high-functioning and would likely test borderline now, having been taught many of the age-appropriate social skills.

She is obsessed with Pokemon cards. Although I'm not at all familiar with how the game is played, she routinely takes out her collection, arranges and looks over them, and occasionally asks me a math question based on the card values that is beyond her grade level (eg. what is 300 times 7)...

She looks at them for some time, re-sorts them, and then puts them back into her book. The regular activity appears to both relax her and bring her joy.