Naina scold Dilip for lying with Angad about the truth. It's not clear if Dilip had an afair with avantika for money. It was not clear that who made Rs.15 crore policy in Rishi's name but Dilip planned and forced Naina to join hands with him in his plot for the money.
Naina also told that she was very humiliated seeing Dilip with Avantika together. She tolerated their illegal relationship for money. Dilip put Naina in avantika's house as governess to rishi. Naina must had brought up angad/rishi from the birth. That's why she's more attached to him though she's money minded. She recognised his talent and brushed him towards making him rockstar and earning money on him.
Whatever Naina's nature was changed along with the 'actor(ess)'.