Angelina Jolie is upset about Jane Pitt's stance on gay marriage.

Jane - mother of her fiance Brad Pitt - recently wrote a letter to her local paper in support of Republican presidential candidate Mitt Romney in which she revealed she doesn't support same sex marriage or abortion, and her views have reportedly left Angelina angry.

"Jane has never wanted to talk politics with Angelina. She knew it would cause greater issues for them, and she wanted to try to have a relationship with the mother of her grandkids. She never thought her letter would be such a big deal," a source said.

Angelina and Brad are two of the most prominent gay rights campaigners in Hollywood, and at one time the actor stated he wouldn't marry the Salt star until same sex marriages were made legal across the US.

If Brad won't try to change his mother's opinions, Angelina is ready to step in to try and convince her future mother-in-law to change her views. "Angelina has told Brad he must educate his mother, but Brad is too much of a mama's boy. If Brad won't do it, Angelina will have to take matters into her own hands and talk to Jane about how, as the mother of such a prominent celebrity, she shouldn't be writing letters that clash with her son's personal opinions. It'll inevitably end up in a huge blowout, with Brad stuck in the middle. Brad keeps telling her not to take this so seriously, but when Angie sets her mind on something, there's no talking her out of it," the source added.