Flag I think Aarti expected that..
If she did not then she would be as blind as Yash...
She definitely knew that Yash keeps Arpita's things so neatly not a particle of dust on anything. more over he does not like anybody to touch it. Knowing all these she went on taking the risk... Of course she knew the outcome as she was hesitating so much to take Arpita's stuff but she played her gamble.. She definitely knew she won't be accepted by Yash in no way but she wanted it to do for Palak so that she atleast can enjoyher birthday but when Yash is accepting her as his wife how his daughters can accpet her in place of their mom???
Palak keeps on saying step mom... no one corrects her as Yash is not telling her that this is your mom as he is not ready to accept Aarti in that role..
If he does not wanted a mom He could have live in Nanny for his daughters and not a mom and official wife... But Pa Scindhia definitely knew what he was doing when he forced Yash to marry. He wanted him to come out his "Arpita Obsession" and live normal married life. He even is thinking about his grandson... and that is funny as his son has not come out of dead to live with alive...