How can I get to the dormitory?

Hint 1 of 3:

The dormitory is where Sarah's boyfriend lives.

Hint 2 of 3:

If you read the hints in order, you should know that her boyfriend plays
rugby.  Go to the rugby field and see what you can find there.

Hint 3 of 3:

You'll have to find her boyfriend and prove he's been seeing Sarah.  Both of
those questions are covered in the "Sarah's Boyfriend" section -- under the
question "Who is Sarah's Boyfriend?"