Unsurprisingly, it was apparently British actor Rob who called time on the relationship.
Rumours started circulating about trouble in paradise after Rob celebrated his 27th birthday without his girlfriend.
Kristen, 23, was spotted looking very glum in a car with a friend, while Rob was off having dinner and drinks with other people.
The vampire duo were also set to attend Cannes Film Festival together and follow it up with a holiday in France, yet neither have been seen there at all.
A source told The Mirror: “Things have been tricky for a while now but they’ve both tried hard to keep things together.
“After nearly four years, neither party was prepared to just throw in the towel.
“But Rob decided he needs to be single for a while and to get his head sorted. He basically needed some ‘him’ time.
“Everywhere he goes there are reminders of Kristen’s infidelity, and it all got a bit much. They’re still in touch though, and are planning to meet up to talk things through in a couple of weeks.”
One of these reminders probably came when Kristen was spotted getting into a car with a mystery man.
Friends assured the press it was the parking valet after rumours circulated that it could have been Rupert Sanders, the man Kristen was unfaithful with last summer.
Rob, who was away at the time Kristen was spotted with the valet man, returned to LA immediately and he did not look amused.
The couple has obviously both been trying to make it work since Kristen cheated with the married director back in July 2012.
But when things happen, like bumping into Rupert’s ex-wife Liberty Ross at Coachella, it's hard to forget.
Following Kristen's exposed fling last summer, she publically acknowledged her then 'secret' relationship with her co-star and apologised for her actions.
She said: “I’m deeply sorry for the hurt and embarrassment I’ve caused. 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.”
Will this break-up be the one that sticks?
With these two you never can tell - they can't seem to keep away from each other and may well be looking as loved up as ever before we know it!