SHE(TIA) decides to push Robin underwater and to go and to have a chat with Anika...
If ever Robin dies due to asphyxia it is all because of Tia action and decision instead of Tia getting revengeful on Annika instead of her thinking that it all happens because of Annika who not ever touches Robin Tia must be arrested by the police(this is not law in India??)
Police investigation must not start right away after getting Robin body in the water, the first to get investigated must not be Tia the one who was with Robin in the pool??
So how is Tia going to get revengeful on Annika?