When first time she saw and recognized Ballu...she should have told the same to Padmini but looking at the issues in family Trishna didn't told the truth to avoid any further tension to Padmini n family.
Second time, she gone too selfish thinking of her own dreams of becoming a actress and for that the poor girl thought that Ballu didn't recognized her and then there will be no issues for her and family...so she went ahead signing the contract.
Then after getting movie and signing amount she kept the truth hidden for two reason, to keep Padmini and family tension free and to fulfill her dream of becoming heroine at any cost.
Mad girl was knowing how cruel Ballu is and still she given more importance to her dream and for that she should be punished. As she hide truth from family...Ballu get chance to ruin the occasion and was almost killed Madhu...along with family. Everyone gone through horrible conditions during Ballu act.
So Trishna is equally responsible for all this things and she should be punished. Paddu and Shammu should give her plenty of tight slaps and even Madhu too give her slaps as Trish always keep jealousy in her mind and always called herself as 'Soutaly' even if Padmini or Madhu never considered or called her 'Soutely'.
Family should not talk to her for sometime so that she can understand importance of family and values.
Along with Trishna, Roma should be confronted as she is the one who banged Trish's brain since her childhood and put a dreams of become heroine.
Sorry for long post.