How can I look around Anna's dressing room?

Hint 1 of 4:

You need to get the opera's owner on your side first.  Make sure that she
knows you're investigating Sarah's murder.

Hint 2 of 4:

Ask her for permission to look through the room, and hand her note to the
manager of the opera.

Hint 3 of 4:

Watson will suggest a way to get rid of the manager so you can poke through
her stuff.

Hint 4 of 4:

Wait until you leave and talk to him once you're out of the dressing room.