According to Entertainment Tonight:
Following the popularity of the first Twilight movie, Taylor Swift begged that she make a cameo appearance in the sequel, New Moon.
Director Chris Weitz explained on The Twilight Effect podcast, (quote) “Taylor Swift and I had the same agent at the time. He told me, ‘Taylor would like to be in this movie. She’s a Twi-hard. She’ll take any role like someone at the cafeteria.’”
The director turned down Taylor Swift because her appearance would be too distracting to moviegoers. (quote) “The moment she walks onto the screen, nobody is going to be able to process anything for five minutes.”
At the time New Moon was released in the fall of 2009, Taylor and Taylor Lautner were dating. Though the relationship was brief. By the New Year they’d split.