true..she does not have the "claim' ...she cannot call anyone "mamma" or "papa" as Tammy or her other friends or pals can call or have parents who they refer as 'mamma" or "papa"
I think the question is more in Khushi's mind..
no matter how much love they shower on her she would still miss Sadhna..Wouldn't she want to know what her mother was like...
Or how Alekh would behave if he were normal..
she may feel a lot of Love and gratitude for Ragini and Anmol and may think she doesn't have the same claim as Tammy on them..
Poor kid..