A Bad Word

Sometimes I wonder if I'm raising a teenager or a toddler.  She has started to say something that I told her is not good, and she has to stop saying it.  What is so bad?  Those words that I know I frequently uttered as a teenager, "I'm bored" or "That's boring".  Yesterday we were outside blowing bubbles, and between the bubbles she kept saying it.  I have no idea why because she loves to do that, and its not an everyday activity.  She has an amazing vocabulary, with great sentence structure and has great comments in context.  I want her to continue to enjoy and explore.  I don't think she was actually bored, but she said it so sincerely.  So I'm going to treat those phrases as bad words, and work on teaching her other things to say should she mention the dreaded "b" word!