Being aware of the words you use when speaking and thinking is a very important step towards self-improvement. It's very easy to slip into using language that's not yours or a language that doesn't sound natural. Sometimes people can be really polite, but they're not aware that they are using abusive language. Others can be really rude, but they're not aware that they are using poor manners.
This can lead to a whole host of problems in social situations and relationships. For example, if you become aware of your language you'll stop yourself saying things like, "Are you upset?" or "Don't talk like that."
When you become conscious of the words you use it will be easier for you to say, "You're being rude." Or perhaps you'll change the way you're speaking to her if she's talking to you. You can't expect to change other people's thinking or their actions without changing your own. How are you going to learn how to speak politely when other people are being rude to you? It just won't happen.
But that doesn't mean you have to be rude. In fact, being conscious of the words you use when speaking and thinking will help you communicate better with those around you. And it'll also help you understand why they are saying what they're saying. This awareness can also help you improve your own behavior. For example, if you make the mistake of saying something because you expected it to be spoken in a certain way, you might realize later that you said something you didn't mean.