nandini died before so if kunal placed nandini's pic then her pic would also be there.Radhika didn't place I don't know why but it is not mishti's responsibility to place to nandini's pic.
Kunal didn't want to hurt his mom! The most he can do is place it in his own home where his mom wasn't there. He can't impose Nandini on her. Similarly Pari can't impose Nandini on them either hence she too keeps quiet. But I place the responsibility on Radhika - she shud acknowledge Pari's mom.