The F Word

So we were walking back home from our usual "T" stop at Coolidge Corner in Brookline last Friday and out of nowhere, the little one said THE WORD, loud and clear. I did a double take and asked her what she said, and she gleefully repeated it. MJ, who had his skull cap on, didn't quite hear it properly and said "What did you say?" There was no doubt about it, she'd said THE F WORD! We didn't freak out in front of her, but my heart was racing and the clogs started churning in my mind, thinking how I should handle this situation. We decided not to say anything because she obviously doesn't know what it means, and we felt that by telling her not to say it, she'd only want to say it even more. Meanwhile, both MJ and I were conversing in Mandarin, thinking how we should tackle this problem at hand. He told me not to make a big deal out of it and it might've been just a one off thing, though I don't know why it suddenly passed her lips, without any trigger.
The word is used fast and furious in this part of the world. You can hear it at least once in conversations between people on the train, walking past you in groups, in restaurants, etc. It's nothing abnormal or shocking about it here, and to tell you the truth, I've gotten used to it and accepted it as part of the English language amongst people here. But when a four-and-a-half year old, your own daughter, no less says it, it's a different matter. She hasn't repeated it so far. We will deal with it and explain it to her if she says it again. We hope that by not letting her hear the word, she will forget it and not repeat it. It's not easy though, cos we just heard it again today when a guy who was talking to his wife, in front of their children, used the word uninhibitedly. I quickly try to distract Meg once I hear it, so hopefully it doesn't register in her mind.
On another note, she's been getting very rebellious lately. She won't listen to me, even after threats and a raised voice. It's highly frustrating for me, knowing that I have no control over her. And all this at the young age of 4.5 yrs! I dread to anticipate what it will be like in her teenage years! I'm definitely stopping at 1!