After Boast Busters, Trixie stuck around, if not entirely by choice. Follow her attempts at working out her relationship and tertiary participation through season one.
When Trixie is hospitalized with amnesia, there are only six ponies up to the task of bringing Trixie back. To bad the mare is absolutely terrified of them.
Following the events of Boast Busters, Trixie decides to hide from the town (and Rainbow Dash in particular) by taking cover in the Everfree Forest. Not every problem can be outrun, and sometimes facing them can have unexpected consequences.