Jennifer Aniston & Justin Theroux's Surprise Engagement: Inside Her Ultimatum!

When Jennifer Aniston and Justin Theroux announced their engagement on Aug. 12, the news shocked many of their close friends. Yes, the couple were nearing their two-year anniversary, but their relationship had been strained lately.

OK! GALLERY: JENNIFER ANISTON AND JUSTIN THEROUX ARE LOVED UP IN ROME

In fact, as Star reported last week, Jen had even called it quits with Justin in July, following fights about marriage and her heartbreaking discovery that he had been meeting with his ex-girlfriend of 14 years, Heidi Bivens, behind her back. So how did the couple get from a tearful end to a new beginning? It took Jen’s walking out on Justin to finally spring him into action.

As Star reported, Jen and Justin’s relationship reached a breaking point on July 11, after an emotional dinner out with friends. She was getting ready to leave for North Carolina to begin filming We’re the Millers, and she issued him an ultimatum.

“One of the last things Jen said before she packed up and left Justin was, ‘Put up or shut up,’ ” reveals a friend of the actress. “She’s sick of his excuses and him dragging his feet on marriage.” That night proved to be a do-or-die moment for Jen, 43.

OK! GALLERY: JENNIFER ANISTON AND JUSTIN THEROUX HOLD HANDS IN PARIS

After almost two years together, there was nowhere else for their relationship to go: They could get married or break up. Justin’s refusal to pop the question — especially during their romantic European holiday in June — was, to her, his choosing the latter option.

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