I don't think Kapoor won't ever think or won't feel regret. She just thinks that regretting her actions means regretting having her family and that makes her very guilty. So it's more "I promise myself not to regret" than really not feeling anything. It's trying not to regret.
Her family certainly has its downs, too, but this is one of the times when they can all be together, so they enjoy their time.
Having her family whole must make her additionally happy. Even if her father will always remain a bit reserved toward her husband, they at least can be in one room and behave in a civil manner.
Thanks for reading