While I agree that Marie should not talk to the media...I am not sure I agree that she is not "princess material."
You would think in the year of 2007 (since 2006 is pretty much over) she would have learned from previous "non royal" girlfriends (Kate, Maxima, Alexandra, Mary, a couple of Felipe's old girlfriends and heck...Koo Stark!) not to say anything...the same thing goes with her father. But her lack of media "finesse" if anything tells me that the relationship is not that serious...she should have been coached by Joachim to just smile politely and say nothing. Also, it is a tad unfair that we (and by that I mean the royal watchers) expect these girls to just pop up and know how to behave, talk and dress like a princess. They are entering a new world of class, traditions, money, expected behavior, etc. Unless you are a part of the nobility (calling Mathilde) you don't just know what to do. It takes time, a good mentor, some media training, and a nice clothing budget.