When did Miss Green become a swimming stars

M: Congratulations on breaking the records at the recent Olympics, Miss Green!
W: Thank you, Mr. Rarker.
M: Oh, look at those trophies ! You became a swimming star at the age of fifteen, didn’t you?
W: Yeah, you’re right.
M: Could you tell me something about your plans for the future?
W: To tell you the truth, I’m going to give up swimming from now on.
M: I beg your pardon?
W: I mean I’d rather not swim at all. I’m too old to...
M: Excuse me, if I’m not wrong, you’ve only twenty now. Is it too old at twenty?
W: Yes, too old for a swimmer. If I swim in an international competition, 1’11 hardly be able to win.
M: But...er...don’t you enjoy swimming?
W: Certainly, and I enjoy visiting other countries, and the Olympics are very exciting. However, I missed more important things.  I had to work very hard at swimming.  There was training before school, after school, and at weekends. While other girls were growing up, I was swimming, swimming. But life isn’t merely swimming, is it?