Kristen Stewart. How could you do it?

“Twilight” fans around the world are asking that one question in disbelief today after Stewart issued an apology on Wednesday for cheating on her co-star and long-time beau, Robert Pattinson.

In a confession made via People magazine, the 22-year-old actress admitted to having an affair with British filmmaker Rupert Sanders, 41, Stewart’s director on the 2012 fantasy flick “Snow White and the Huntsman.”

The confession came after Us Weekly magazine obtained embarrassing photos of Stewart with Sanders.

“I am deeply sorry for the hurt and embarrassment I’ve caused to those close to me and everyone this has affected,” Stewart said in a statement.

“This momentary indiscretion has jeopardized the most important thin in my life, the person I love and respect the most, Rob. I love him, I love him, I’m so sorry,” she said.

Sanders quickly followed Stewart’s mea culpa with his own public apology, which he directed to his wife of seven years, Liberty Ross, and their two children.

"My beautiful wife and heavenly children are all I have in this world. I love them with all my heart. I am praying that we can get through this together," said Sanders.

As expected, the fallout from Stewart’s “momentary indiscretion” is making headlines around the world.

Pattinson, 26, is said to have been left “heartbroken and humiliated” by Stewart’s dalliance with Sanders, according to reports in the New York Post.

Sander’s 33-year-old wife also took to Twitter to share her thoughts on the scandal, reportedly tweeting the words “wow” and “sometimes bad things fall apart so better things can fall together” before she deleted her account.

But fans of Stewart and Pattinson, arguably the hottest young couple in Hollywood today, are still showing their support for the stars during this crisis.

"Though I am hurting, I'm calm. I love Rob. And I will always love Kristen. Until then, in spite of this devastation, I stand by #Robsten," tweeted fan @Ate_Ofie.

"Kristen, wherever you are, I love you, and I'll always be your fan. Rob, hold her tight, she needs your love. Robsten is Unbroken," were the sentiments shared by @stewransom.

Some fans were not so forgiving of Stewart’s betrayal, however.

"Am I the only one who finds it so funny how Kristen Stewart cheated on Rob Pattinson with a marred 41 year old man Luke um ew (sic)," mused @TheStylesVoice.

Others also used Stewart’s current troubles to mock the Hollywood starlet and her acting abilities.

"Unfortunately Kristen Stewart can't show she's sorry for cheating on Robert Pattinson because she has no facial expressions...," tweeted @GobletOfTweets.

"I would like to apologize to Kristen Stewart for the momentary indiscretion of falling asleep during NEW MOON," @DamonLindelof wrote.

It is yet unclear how Stewart’s fling with Sanders will impact the November release of “The Twilight Saga: Breaking Dawn Part II.”

Since the franchise’s debut with “Twilight” in 2008, fans have embraced Stewart and Pattinson and the living embodiment of Bella Swan and Edward Cullen, the star-crossed lovers in Stephenie Meyer’s Meyer’s teen vampire books.

Indeed, Twihards have come to think of Bella, Edward, and the actors who portray them like family since 2008 -- a sentiment which has helped the film franchise to gross more than US$2 billion to date.

In 2012’s latest instalment directed by Bill Condon, newlyweds Bella and Edward bond even more deeply as they try to protect their child, Renesmee, from The Volturi coven of vampires.

Fans will also see Bella explore her new life as a vampire and all the new dangers accompanying this transition in the upcoming “Twilight” entry.

Though news of Stewart’s surprise affair has disappointed some fans, it is unlikely to cause worldwide boycotts of the movie in November.

Scandal sells in Hollywood, and Stewart’s fling with Sanders could help lure more moviegoers into theatres to see the conclusion of “The Twilight Saga: Breaking Dawn.”

As for Stewart’s bankability at the box office, it is unlikely that this public disgrace will hurt the actress’ bank account.

In June of 2012, Forbes named Stewart the Hollywood's highest-paid actress, earning an estimated $34.5 million from May of 2011 to May 2012.  That sum now places ingénue Stewart ahead of Angelina Jolie, Cameron Diaz and Sandra Bullock.