TARA only has to get caught by bank, police and Amruta.
How much ever loopholes visible to us in cheque fraud, but still writers were careful to save Rajeev from beginning. He has to stay back in story to later take double revenge on Amruta? for losing his love interest as well as easy money looting opportunities. 
It's Tara who practiced Virat's signature, she stole his cheque book, forged cheques with his sign, went to different Mumbai branches of Indie bank in person, created fake id of Amruta's bank identity to show as some silly proof to cashier, changed her looks to fake appear as Amruta, withdrew huge amounts of cash more than once, carried those heavy cash bags in person out of bank,
later deposited that cash into her personal bank accounts, ofcourse spent some parts of that cash lavishly.
Now income tax dept also has to send notices to her.
Rajeev is NOWHERE in picture in the forefront,
and Tara won't possibly take her lover's name as he has to be safe outside, to bail her. Even if Tara takes Rajeev's name as mastermind of fraud, he will deny saying after marrying Nimrit he left Tara, so she is framing him out of vengeance.

why she