Err, apparently she and Taylor Lautner got it on..
If you thought Robert Pattinson and Kristen Stewart were about to get their happy ever after you might want to sit yourself down as the couple will be waking up to a fresh batch of rumours about the actress and her alleged cheating ways this morning.
According to US OK! Magazine, that car kissing "indiscretion" with Rupert Sanders wasn't the first time Kristen has strayed and apparently she's been involved in several other on set trysts during her time with Rob.
“When they first got together, she was going back and forth between Rob and her ex-boyfriend Michael Angarano,” an insider told OK! magazine.
“Eventually she did end it completely with Michael, but it went on or a lot longer than Rob ever knew."
While she did end things with her ex, it's rumoured that one of the biggest factors was that she and co-star Taylor Lautner were actually getting it on, although how they could possible have managed that right under Rob's nose we really don't know.
"Everyone knows about their friendship, but not very many people know how close they really got," the source continued.
"She even lied about it to Rob."
Blimey, this is all starting to sound a little bit like Twilight isn't it? Next thing we'll be hearing that both of them have grown fangs and are being pursued by some very pale looking blokes in capes.
"When she worked on Welcome to the Rileys, she had a full-on fling with one of the production assistants. Luckily the guy had a girlfriend, so he was just as paranoid as she was and they kept it pretty well hidden."
We're not sure how we feel about all this, especially as Rob and Kristen were spotted earlier this week looking very cosy indeed.
What do you think about these rumours?