New cheating fears erupt sending JESSICA BIEL into a jittery panic over fiancé JUSTIN TIMBERLAKE’s new hottie costar – Bond girl GEMMA ARTERTON.

Jessica, 30, flew to Justin’s side, because she fears another woman will try to steal him away before their wedding, say sources.

“Jessica worries because Justin is such a flirt,” a source told The ENQUIRER. “So she flew to Puerto Rico where he’s filming ‘Runner, Runner’ just to keep an eye on him.

“Justin is a charmer who can’t help but attract stunning girls. While Jessica thinks he’ll behave himself, she finds it hard to trust other women with him.”

Adding to the temptation, Justin’s co-star is Brit­ish beauty Gemma Arterton, who made a big-screen splash in the 2008 James Bond film “Quantum of Solace.”

“Gemma is a brunette, and Jessica knows she’s Justin’s type,” added the source.

“She told Justin that she was joining him because she hates being away from him, and that’s true.

“But deep down she also feels that she needs to keep tabs on him before their big day. She doesn’t want her dream wedding ruined!”

The couple reportedly got engaged in late December 2011 after an on-and-off five-year romance.

AS THE ENQUIRER previously reported in April, the “SexyBack” singer’s be­havior rocked her family’s trust in him.

“Justin refuses to sell his bachelor pad on Mulholland Drive, and that’s left a foul taste in her dad Jon’s mouth,” a source revealed.

“Justin insists he wants to keep his boys-only parties away from Jessica’s house, where he normally stays. But even when Jessica offered to build a ‘man cave’ on her property for him, Justin refused to sell. As far as her parents are concerned, these are not the actions of a man who’s serious about settling down.”