Not only during the Mandaar track her approach to Sunny in earlier episodes was also wrong to some extent. The trick she played to postpone engagement was totally unnecessary and in a sense was a betrayal to Keerti. Up until that moment Keerti had treated her like a friend for whom she was ready to go against her own brother.
Do we not remember how she was when it came to punishing Mandaar's murderer? She used no tact and was not calm at all until R-P both ended up in jail. She was right in seeking justice but she wasn't tactful with Keerti and went ahead and antagonized her because she was angry that time (which she had the right to be). That was her approach.
This time it's different. There is an aspect to the Rao family history that Pallavi doesn't know about which Amma and Raghav do, so until Pallavi discovers what it is, she'll be in the dark about how best to handle this. Frankly, I'd rather she stayed away from Keerti's matter in terms of her marriage. She can focus on Sunny if she wants to (we know it's inevitable).
As for Amma and Raghav's approach here.... ugh totally totally wrong.
During Mandaar track she turned completely selfish and turned a blind eye towards pain of all members of Rao family especially Amma.