"How proud we are of her, being a single mother (of) five kids," Shriver told a group of fellow guests at a quinceanera party honoring the mistresses' niece.
Housekeeper Mildred Baena, the woman who delivered Schwarzenegger's love child just one week after Shriver gave birth to her youngest son Christopher in 1997, accepted the accolades as she stood beside the two-timing "Terminator" star.
"Five kids, raising all of them, putting food on the table, keeping her job 10 years, showing up day in and day out," Shriver continued, clearly unaware that the youngest of the brood belonged to her husband.
"(She's) doing an incredible job," Schwarzenegger chimed in.
Video from the family celebration aired Monday showed Schwarzenegger, Shriver and their two daughters receiving communion during the quinceanera mass and their oldest son Patrick escorting the love child to the alter for a blessing.
The blond-tressed boy, then about 4 years old, danced and smiled in a tiny tuxedo in footage from the after-party obtained by ET's sister show The Insider.
A relative told ET that contrary to an earlier report, Schwarzenegger did not pay for the extravagant coming of age party. He added that the boy grew up thinking his dad was Baena's ex-husband, the man listed on his birth certificate.
Mildred Baena, 50, has been in hiding with the boy since her stunning secret and Schwarzenegger's breathtaking betrayal made front page news last week.
Schwarzenegger said in a statement that he "told" Shriver about the dalliance after leaving the governor's office last January, but Shriver reportedly acted on her own suspicions and got a confession by confronting the trusted household staffer, RadarOnline reported last week.