Random thought...
Dhruv returns to the 21st century. Accidentally sees a photo of the Maharani in his house and reacts. His mother then puts two and two together, and insists that she travel with Dhruv when he goes back to the 17th century.
Which leads to Susheela and Mr.Susheela's re-union, and consequently D & T's mini separation because Sushi gets mad at T and Maharani.
Alternatively, you could say the Maharani might recognise Susheela when she sees the family portrait that Tara has, and then understand that her doctor companion is Susheela's husband.
But Sushi recognising as per my quoted post and consequently time travelling would probably make greater sense- there's little the Maharani can do in her quasi imprisonment state if she discovers the truth first.
Plus it would fit my "you need someone from the present to travel back to the past" theory (Sushi going with Dhruv)
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