If you are planning a visit to Stockholm during your stay in Annika's house, here are some tips:
From Hallsberg, a small town located 15 km from the house there are very good train connections to Stockholm.
If you book in advance before the scheduled
departure, one can find traintickets from Hallsberg to Stockholm for 95 SEK/person.
Here a link to SJ (swedish railway) where you can book your ticket:
https://www.sj.se/en/home.html#/
Stockholm turistguide:
http://www.visitstockholm.com/en/