There are 2 if my personal favorites. These are permanently in my reading list so I can directly give you the title.
1. Tu jo Mila
Here Khushi's step mother and step sister plot to replace her and enter the rich Raizada house. They succeed but in the confusion Khushi is married to Arnav and there starts their magical journey of life while her step sister downfall slowly starts. Story handles post partum depression in the final few chapters which is a good idea. Story has a wholesome feel good ending.
2. Zero Clarity
First and only paranormal fanfiction of ipkknd.
Arnav's mother is killed and her soul is trapped by their enemies. Khushi enter RM under bizarre circumstances and then strange things starts happening in RM. Khushi is pictured as a girl with divine blessings and helps aid in fighting dark forces. In the process arshi also get married, they defeat the dark forces and send arnav's mother's spirit into light..another feel good, good triumphs over evil story.