Roommates should respect each other's rules and boundaries.
Jeanette and Nina have just become roommates so Nina made a rule to always knock before entering her room.
Jeanette wants to talk to Nina.
Jeanette knocks on Nina's door and asks if she can talk to her.
Jeanette bursts into Nina's room, so she can talk to her, and she doesn't bother to knock.
Nina tells her to come in, and they have a nice chat.
Nina asks Jeanette if she forgot about her rule and says that it's very rude to burst in like that without knocking.