"Please go away!"
It's not that she's being polite, or that he's annoying, it's just that everyone is changing.
Outside, she is a eldest sister and an ordinary college student. At home she is a good daughter to her parents and a stupid mother to her son.
Outside he is a boss who wears many hats and a humorous professor, but at home he is silent and cold.
They met because of coincidence, and they separated because of barriers.
She had been a big problem for him, catching him off guard.
Now he was her big problem and she couldn't get rid of him.