Jen An 'unhappy about fiancé's past'

Jennifer Aniston is reportedly not happy that her fiancé Justin Theroux once had a fling with Cameron Diaz.

The Hollywood A-lister and Justin's apparent relationship problems have been the subject of intense media scrutiny, but the couple put on a united front recently while enjoying time out together in New York.

But news of an alleged dalliance with Cameron in 2002, when the pair worked on movie Charlie's Angels: Full Throttle, has seemingly upset Jennifer.

"Jen is angry because she didn't find out from Justin himself. She thought she knew all about his history, and Cameron is a friend, so she was embarrassed to only hear the rumor recently and second-hand," a source revealed to British magazine Grazia.

"It was common knowledge among Justin's mates. It was never anything serious, and they haven't seen each other for ages, but Jen feels disappointed, she didn't find out about it from him."

Jennifer and Justin announced their engagement in 2012, but have yet to set a date to tie the knot. Reports surfaced earlier this month that the couple were looking to arrange a ceremony in Hawaii, but sources fear that the couple could once again face a setback in their relationship. With 45-year-old Jennifer living in LA and Justin currently based in New York for work, distance is also a contributing factor.

"This latest fight hasn't helped. Things are very tense between them and the distance isn't helping. There is still no wedding date set," the insider added.

One person who's hopeful that they'll make it down the aisle is Justin's TV personality cousin Louis Theroux.

"Jen is a nice person. I hope her and Justin do get married, but I don't have any dates or anything like that. It would be nice to be there if they did," Louis recently said.