In S1, Kuki was blind and here she is mute. I feel she will witness Prerna's goodness and others harassing her but obviously won't be able to express it.
It's the classic trope- heroine's source of support that knows the truth but cannot express it. Somewhat similar to Moloy- though he knew Komolika's truth, he couldn't tell his family and Prerna, first because of the coma and then due to being confined to a wheelchair and being unable to talk.
Kuki will probably be Prerna's only comfort during the coming times. Waise every one has a tough time all the time on this show. đ
Yeah that same father in wheel chair hiding secret is shown in IPK too