The Prewitts may have many of the same reputations as do the Malfoys, but there are a few key things that you are lacking in knowledge when it comes to high society: in particular, their status in my world. They are old money, yes, but they are also many other things that make true high society wizards cringe in disgust, such as my own family. Your family means little to me in that sense, Ginny. You don't need to go about impressing me because of your family name. If that mattered between us, I can guarantee that we wouldn't be seeing each other, simple logic there. I mean no offense, but it had to be said.
If you truly want me to be myself, then I will. But it's time they realize that I'm proud of who I am, and I couldn't give a damn what the rest of the world thinks of me. So I'm a spoiled, selfish brat. That's me. And I don't plan on changing that, not if I have a say in who I am or what I do in my lifetime. I'm going to say my snide remarks and my sarcastic comments and not care what people think of that. I'm going to be confident and arrogant and all of those things. If you really want me to be myself, Ginny, accept every bit of me, not the part that you want to see.
In fact, if we really wish to test this, I can come to your home tomorrow, and truly be myself. I highly doubt any of your brothers really have seen me just being, not acting.