Did Kristen Stewart Cheat on Robert Patterson?

Source claims that Kristen Steward cheated on Boyfriend Robert Patterson with "Snow White" Director, Rupert Sanders.

Many say hints of cheating were thrown at the Snow White and the Huntsman Premiere, where similarly dressed Kristen Steward and Rupert Sanders looked incredibly close.

Today, People magazine reported the Twilight actress Kristen Stewart had a brief but romantic affair with her Snow White and the Huntsman director, Rupert Sanders.
The 22 year old actress, whose relationship to  Twilight co-star boyfriend of three years Robert Patterson have entrapped fans for years, has now found a new love in the 41 year old director.  
The director has two young children with model Liberty Ross. According to reports, Kristen and the director of the film started the romance during the filming of the Disney blockbuster. However she felt incredibly guilty after cheating on Robert Patterson, who had recently hinted at marriage.

In interviews during the Snow White and the Huntsman promotional tour, the director showered praise on his leading lady and supposed lover, describing her as "a great spirit, [Kristen] really quite rebellious...and feisty and kind of wild".

Stewart has yet to respond to the rumours but we know her now boyfriend believes strongly in fidelity and being monogamous. He infamously proclaimed "Life is not black and white...there is one thing I never understood: why people cheat" in Italian Vanity Fair in 2011. Well if these rumours are true, the relationship will become like their fan favourite characters - Dead and desperate for blood!