Yes and I believe that's after the Vat Savitri puja or like right before it. Regardless, that happens after Pallavi gets to know about the Keerthi incident. You tell me, why would she take the responsibility of protecting someone's reputation that she's known for a few weeks versus someone's reputation that she's known for two years or even more?
Just like how she was willing to send Keerti to jail whom she knew for many years as her best friend and then as her sister in law for the death of Mandaar (whom she knew only for like may be 3 or 4 months or something?)