Slowly, and gradually Aarti had begun to think that she was indeed the Dubey's daughter, but a few scenes in the past few weeks have made her question this - and she is now beginning to think that she is well just a daughter in law. When Shobha ma asked her yesterday, if Aarti doesn't trust her anymore - thosewere some big words. Shobha is actually emotionally blackmailing Aarti to keep Ansh with her, for the (selfish?) motive of saving Prashant. In a way, Shobha has made Aarti repay what she had willingly done for her. Shobha had willingly sided with Aarti - but by participating and instigating Aarti in a lie situation that is separating Aarti and her son, and may cause him physical discomfort - and in letting Prashant in some aspect affect Ansh's and Aarti's relationship for a selfish motive - She has basically evened out with Aarti. Aarti's son is now suffering (and may in the future) as a result of this lie. In terms of a debt, there is nothing more Aarti needs to do to repay the Dubeys. By manipulating her, and lying to her for a thing as grave as an operation on her five year old son - Shobha has stooped to a level whereby Aarti does not ever need to repay her for siding with the DIL over the son.
So in the end, Aarti can just free herself from her past totally and leave them alone - at least that will be justified?