Why Kristin Cavallari and Jay Cutler Broke Up (Report)

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The former "Hills" star and the Chicago Bears quarterback were due to marry next spring.

Chicago Bears quarterback Jay Cutler and former Hills star Kristin Cavallari have split up and a friend says she knows why.

Cutler was "too controlling" over the reality star for their relationship to last, the unnamed friend told People magazine: "Jay Cutler was beyond controlling and didn't really like Kristin to go out. When she did go out, he called all the time and demanded to know exactly where she was going and who she was with.

"He made her choose between him and being friends with a lot of her girlfriends. I'm not surprised it didn't last."

They had been engaged since April and were planning a 2012 wedding. Wedding plans had progressed to the point that they had already celebrated with an engagement party earlier this month and had signed up for a gift registry.

As word spread about the split, Cavallari tweeted Sunday, "Thanks for the support. Love u guys." Cutler's Twitter account has been mum on the subject.

Cavallari rose to fame in reality TV but has since dabbled in acting with appearances in ABC's The Middle and CBS' CSI: NY.

Cutler spent three seasons with the Denver Broncos after the 2006 NFL draft before being traded to the Bears in 2009.