Due to some circumstances always Priyanka had to do sacrifices. That's why she hates her mother. She is not able to forgive Kusum after so many years. Then Juhi, She blames Juhi. Because of who she made a fool in front of Tarun. She is still not able to forgive Juhi, even though she is behaving so nicely to her.
Then why she is forgiving Tarun, who insulted her two times. She is feeling bad for him. He insulted her in front of the whole office. If somebody would insult me in such a way, then I would not like to keep any relation with him/her.
How is trusting Tarun who doesn't respects his mother? Didn't she see the OSCAR WINNING MONOLOGUE Tarun gave in her house to insult her mother? Not once but many times.
After Helping Tarun, when she heard that how much Preeti trusts she felt guilty. If I was Priyanka then I will apologize to Preeti not tell Tarun that I cant help him. No wonder if she does a murder to help Tarun (As Tarun said)
Just can't understand that she can't forgive Kusum and Juhi, but is forgiving third class Tarun. Kusum and Juhi love her so much then also she is rude to them.