okay i think ganga is the killer... in history, nandini had killed gujral to save bhoomi... tulsi killed ansh to save nandini... it could be that ganga kill tripti to protect her family.
besides she should be back by now. i know she isnt supposed be in india during the murder but this is ekta anything can happen. ganga might have even turned in to superwomen and flee her way back to india.
i wonder why she even went there, because technically rishab is a fraud, and for that reason i doubt he has ever been out of country. and if he hasnt been out of country then how the hell would ganga find information abt him in london?😕