If you missed the first part of the interview posted by nyyhoneybee yesterday here at the main community...
Here is the article and please do not read it if you have not read Deathly Hallows as is it does contain SPOILERS about the book.
The video of the interview is now online at the link above.
In the second part of the Today Show interview, JK Rowling explains why she changed the last sentence of the book, where in the original ending the last word would have been "scar." In addition, Jo discusses what house she would be in if she had attended Hogwarts and what she would see in the Mirror of Erised.
"I would definitely see what Harry sees. I would have seen my mother. I would be able to have a conversation with my mother. [Her death] had a profound influence on the books...from that moment on, death became a central if not the central theme for the seven books. In many ways all of my characters are defined by their attitude to death or the possiblity of death."
You can find this article and video here. Remember there are SPOILERS in this interview, so do not view it if you have not read Deathly Hallows.