Twilight fans were hit hard last night on all gossip fronts with news of an alleged affair between Kristen Stewart and married-with-children director Rupert Sanders who is 19 years her senior.

Stewart, who is romantically linked off-screen to her on-screen partner Robert Pattinson, has allegedly been spotted in the midst of a "marathon makeout session" with Sanders, who directed her in Snow White and the Huntsman.

Photos of the tryst, which supposedly took place on July 17th, appear in this week's Us Weekly. People Magazine's latest issue covers the same story with the addition of a quote from a source who says "Kristen is absolutely devastated" and that it was "a mistake and a complete lapse in judgment" and a "fleeting moment," not an affair.

Stewart and Pattinson were last seen together at Sunday's Teen Choice Awards looking fairly cozy.

So far no official comments from Stewart, Pattinson, or Sanders.

UPDATE: See leaked scans of the "incriminating photos" over here.

UPDATE 2: Kristen Stewart has just released this statement to People Magazine, apologizing to boyfriend Rob Pattinson for "momentary indiscretion":

I'm deeply sorry for the hurt and embarrassment I've caused to those close to me and everyone this has affected. This momentary indiscretion has jeopardized the most important thing in my life, the person I love and respect the most, Rob. I love him, I love him, I'm so sorry.

[images via Getty, Us Magazine]