ET has the latest...

Following the battle of the engagement bling (she says she's keeping it, he thinks it should go to charity), reasons behind the 'Bachelor' break-up between Matt Grant and Shayne Lamas are now being revealed.

"I'm used to the Hollywood BS," Shayne, the daughter of actor Lorenzo Lamas tells Us Weekly. "But it really got into Matt's head."

But sources close to Matt tell Us a different story. "After he moved to L.A. and saw her constantly partying and clubbing, he realized that she wasn't behaving like a woman who was ready to be in a serious relationship," the source says.