Somehow Garima's fear towards Arnav's Dadi made me think she is the love interest of Arnav's dad. Khushi might not be related to Garima at all.
Does khushi's insistance to Arnav to call Garima as Amma have some significance? Arnav said he does call anyone else as his mother.
Just a weird thought came to my mind which I wanted to share. Probably I am completly wrong and think too much of IPPKND :D