There might be a good reason why Jennifer Aniston and Justin Theroux have been engaged for nearly three years now but are yet to set a wedding date together. There's a new report that suggests the Hollywood pair is going through a crisis in their relationship, with sources saying that Aniston thinks Theroux doesn't appreciate all that she has done for his career.

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According to the popular blog Celebitchy, things have reportedly gotten so bad between the couple that Aniston is supposedly telling her friends that Theroux treats her like she's his "arm candy." Apparently the actor is using her for publicity and has been urging her to do a cameo in Zoolander 2.

"Jen's ready to pull the plug on her cameo after 'an inch became a mile' with Justin's demands," a source suggests. "Justin and Ben [Stiller] want to go to ComicCon and do some publicity stunts for the movie and he's been begging her to get involved. Jen's already agreed to do a small cameo in the movie, but lining her up for some cheap publicity trick is not how she wants to roll anymore."

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What's more, Aniston is apparently "not willing to work on anyone's career at the expense of her own." The actress has worked hard to distance herself from her comedic roles for more serious ones on the big screen.

"Expecting her to line herself up for a prank when she's desperately trying to find a serious dramatic role is not fair," points out the insider. "Justin forgets just how much she's done for him. He should be grateful she's agreed to do that cameo, not demanding more."

So far neither Aniston nor Theroux have commented on the report.