I think she is just very confused about what to do. She doesn't know that Antara is autistic, so she's just trying to be the lady of the house and pull her family together. It came out wrong what she said, but she has so many mixed feelings that she's almost helpless. Part her wants to forgive Aditya and move on but a bigger part of her is stuck and can't. I know she is warming up to him because when he was praying that one night, you could see that she really wanted to help him. The next she even asked him if everything was okay.
Well, I also think part of Vidhya wants to warm up and accept her, but then she sees Aditya and remembers that this his affair child. This brings about feelings of anger towards him and guilt towards Antara. Like in today's episode, she ended up asking Aarti, "Agar woh gir jati?' when Aarti was telling her about Antara being on the roof, That showed that she cares for her. Also when Aarti had locked Antara in the room, Vidhya was silent, but you could tell that she did not like it very much. It's the little things that add up and will eventually make her truly love Antara as her daughter.