London, Jul 27 (IANS): Singer Lady Gaga has defended Kristen Stewart for cheating on Robert Pattinson with married director Rupert Sanders, telling people to leave them alone.

Stewart has publicly apologised to her boyfriend of four years Pattinson, after she was caught in a steamy make-out session with her "Snow White And The Huntsman" director Sanders.

"This Stewart-Pattinson stuff is brutal. Makes me sad the way press acts. Hope they are ok," Gaga tweeted, according to contactmusic.com.

"I am deeply sorry for the hurt and embarrassment I've caused to those close to me and everyone this has affected. This momentary indiscretion has jeopardised 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," Stewart said in a statement.

Sources close to the actress insist she was not having an affair with Sanders and it was a fleeting mistake.

"Kristen is absolutely devastated. It was a mistake and a complete lapse in judgment," said a source.

The couple has been dating since meeting on the set of "Twilight" four years ago, in which Pattinson plays vampire Edward Cullen and Stewart essays the role of his love interest, Bella Swan.