Emily Maynard hasn't been flashing her famous smile as much lately -- and who can blame her?

On Tuesday, multiple sources confirmed to Us Weekly that the Bachelorette star, 26, and Jef Holm had finally pulled the plug on their fraught relationship and five-month engagement -- following an ugly August 19 blowout (spurred on by Maynard's sexting with Matt Leinart), Holm's flirty recent night out with another woman in early October, and months of a carefully fabricated, PDA parade for the cameras.

"Emily just decided that she's had enough," one insider tells the new issue of Us Weekly, which details the couple's final breakup conversation and the painful weeks leading up to it.

Adds another pal: "Emily was extremely miserable. She was like, 'I'm dying, I'm dying here.'"

Entrepreneur Holm, 28, changed his Facebook relationship status from "engaged" to "single," and the former pair have also stopped following one another on Twitter.

"She says she and Jef have nothing to talk about," another source explains.

For all the details on the latest Bachelorette split -- how her daughter Ricki, 7, will cope, how they both cheated, their "crazy fights" and more -- pick up the new Us Weekly, on stands Friday!