I have her following reasons for saying Mohini is a viper.
She sent evictions papers to a man who has been a loyal right hand man and scarificed everything to help her husband, just so that his daughter would agree to marry her thrice divorced friend. She knew what she was doing was wrong which is why she hid it from her husband and son.
She tells both her daughters that she does not love them as much as she loves their brother. She also tells her older daughter not to be happy with her husband but at the same time was the one to force them to get married to save face in society. She threatened to kick said daughter out of the house if she does not support her in all her decisions, while not applying the same principle to her son.
She forced her son to go ahead with rhe marriage to Komolika knowing he was desperately unhappy. She could have said no to prerna and still not forced her son to marry someone who he didn’t want to marry. She watched while he suffered and did nothing while also saying his happiness is all that maters to her.
She is treating badly the wife (veena) of a man who gave up his entire life for her husband and who died while with her husband. Rajesh was not there in the car for his business. He was there to support moloy who was confronting komo for trying to poison Mohini (said viper) and ruin his business. Rajesh dies as a by-product of that.
Prerna with vikrant’s help is the one who rescued the Basus from Komolika. Komolika tried to kill moloy multiple times and also planned to put Mohini in an old age. She made this very clear to Mohini. And Mohini is blindly ignoring this great escape in order to torture the Sharmas.
Yes Mohini is entitled to dislike prerna. I don’t agree with her dislike being based on prerna being middle class but I have no included that in the above reasons because I know many people still believe it’s her right to choose her sons partner
I am also putting veena’s over reactions to one side. From the beginning of kasauti 2, the very first episode veena has been shown to be the one most affected by Mohini constant insults. Pretending like she didn’t know prerna name, belittling veena constantly. Veena has finally burst and is now overreacting but that’s another story.