Who knew Bella Swan was such a bitter babe?!

On Monday afternoon Kristen Stewart went off on one of our photographers while taking a lunch break from her new flick Camp X-Ray.

When asked why she is angry, K. Stew mouthed off, "Because you're a piece of s**t. You don't deserve to breathe the same air I do." All this coming from the girl who famously cheated on the uber dreamy Rob Pattinson with a married man? Hmmm...

The Twilight starlet then called our lensman a "f**k face" and looked like she was going to explode when asked about her relationship with Rob.