Does knowing that she is on live tv make katniss behave differtly than she would otherwise?

Katniss knows that if she breaks down, and shows the emotion and weakness she is feeling when Prim's name is called for the reaping, that she will immediately become a target for all of the other tributes. Even though she could possibly defend herself (especially if she is located farther or higher than her opponent, with a bow, in the right terrain), she has no idea what to expect from the other tributes. This also applies to her first interview with Caesar Flickerman.

As for her second interview and third interviews with Cesar, she knows that if she does not act completely in love with Peeta, that her loved ones' lives (and Peeta's loved ones) are all in extreme danger.