Yes, her mother is trying to repent her sins and therefore would like to see Radhika married to Dev, but let us not forget that this is the same mother who turned "villian" while they were at Phool Bangla. This is the same mother who did not hesitate to favor her daughter, Vishaka, when presented with a situation wherein she had to choose, even after she had given Radhika permission to confess the truth to Dev and had even went down on her knees seeking forgiveness from Radhika for her sins. Do you think that she would hesitate again to remove Radhika from Dev's life when Vishaka decide to return home? I think not.
Yes, Vaishali, Dadi, Vivek and Birju would be very happy for Dev at the moment. What were these same people doing while Radhika was being wrongfully accused by Mrinalini and Cha-Cha? What were they doing when she was being "dragged" out of the house? No one stepped in to save her honor, even though it was clearly written in her eyes and actions that she was innocent. Vaishali, Dadi and Vivek are only happy now because they don't want to see their precious Dev in pain, sorrow and being insulted by Mrinalini. Do you think that they would show Radhika the same love and respect they showed to Vishaka? Do you think that they would lavish her with the same praises they poured onto Vishaka, even though they knew that Radhika was the one doing almost everything while they were in Delhi? No, they would not.