She whines and vacillates until Peter and Nick have bought the Idiot, and then throws a giant strop because she's lost her chance.

Really it's Nicola who comes off worst in the horse thing; she buys half a pony, then swops it with Lawrie in return for the complete works of Shakespeare. Lawrie's already extracted a number of valuable items (eg his radio) from Peter, in return for what, I don't know.

Was Peter's and Nicola's purchase of the Idiot subsidised by the adults? That would partly make up for Catkin.