Here she saw how Arnav stood up against a powerful and intimidating woman (Dadi) just to make sure she treats Khushi right and doesnt hurt her. Payal must definitely at that point have thought about how her own husband Akash never stands up for her or defend anyone who badmouths and mistreats her - like the way his mother does every single day.
That feeling must be the saddest one to experience as Payal knows deep down she cannot rely on Akask to protect her or take care of her when and if something happens to her in the future.