I dont think so.
If she really filled in for Naira,
They would not have been craving for Naira like that. They would have closed that chapter and moved on.
They just gave love and care to Gayu. They did not adopt her or gave singhaniya's name to her as for as I know.
Gayu is neither here nor there. She should accept the truth and move on.
Naira lived like an orphan for so many years and Gayu live like a princess in that house. Yet Naira did not feel jealous.
Forget family, Gayu cant see Naira and Kartik together.
Akshara should allow her to go with her dadi than cling on to her and make everyone feel miserable.