Kristen Stewart and Nikki Reed are not frenemies, they are downright enemies.

Apparently Reed and Robert Pattinson, Stewart's current beau, had a fling some time ago and Stewart will never forgive Reed for that. The two were formerly best friends.

Kristen has never forgiven Nikki for the fling she had with Rob, a source told Hollywood Life. Kristen never confronted Rob about the affair, she just put the blame on Nikki and accused her of pursuing him.

Nikki is very vocal about Kristen not being supportive of her success, the source says. Nikki is not one to censor herself to avoid confrontation and Kristen doesn't like that.

Although Reed and Pattinson have remained friends, the sources says that this probably will not last long.

Miraculously, he's been able to maintain a friendship with Nikki. But it won't last, not if Kristen has anything to say about it.

Reed, who recently married Paul McDonald and is in wedded bliss, believes that Stewart has not been supportive.

Nikki is very vocal about Kristen not being supportive of her success.

In an interview with Seventeen magazine, Reed said that filming Twilight was like being at sleepaway camp, adding, it was innocent and fun, and we were like one big happy family.

However, when asked about her relationship with Stewart, Reed did not have as kind words to say.

Success came along and changed the dynamic, she explained. It was very, very sad. Let's just leave it at that.

At a recent taping of Ellen, the Hollywood Reporter noted some visible tension between the two former besties.