In the Bahamas for a long-planned family vacation in late June, Garner and Affleck were going to make a decision regarding their future together, says a source close to Garner. "It was game time," the source tells PEOPLE in this week's cover story. "Ben had already told her he hadn't been committed to the marriage. They were trying to figure out what to do."
Several sources tell PEOPLE that Garner found out while in the Bahamas that Affleck had been having an affair with the couple's nanny Christine Ouzounian for months – an allegation Affleck strongly denies. The couple announced their split on June 30. "There was always a speck of doubt in Jen's mind about separating, but that's now gone," says a friend. "She is very angry. To Jen, this is the ultimate betrayal."
Hired by the couple last spring, Ouzounian, who had nannied for Neil Patrick Harris as well, "was very caring and loving toward the kids," says an L.A. source. But when Garner began filming Nine Lives in Canada, Ouzounian began spending more time with Affleck and "dressing a bit more inappropriately" around him, adds the source.
Multiple sources have told PEOPLE that Ouzounian told friends she was sleeping with Affleck and would often meet him at the exclusive Hotel Bel-Air. ("Not true," says a source close to the actor, who maintains that Affleck and Ouzounian had a "work relationship and a friendship. Ben's friendly, but it's not always meant to be flirty.") Ouzouzian's friend says that "for Christine, it was a real relationship. They had even talked about plans for celebrating his upcoming [Aug. 15] birthday."
"This is not anything she wanted as an outcome for her family or her marriage," says a friend of the actress. "But everyone is rallying around her."
Reporting by K.C. BAKER, LIZ MCNEIL and PERNILLA CEDENHEIM
For much more on Affleck and Garner's difficult split, the nanny allegations and how Garner is coping, pick up this week's issue of PEOPLE, on newsstands Friday