..will not let Vidya slip into a sadful numbness...she is going to be grief stricken but at the same time, she is convinced without any doubt that it is Sindoora's doing. So the need to pay Sindoora back she is going to fight, and therefore she will find her strentght in trying to bring Sindoora down.
I don't think she will be cold-hearted, or lose her original chracteristic, but as Saagar himself said, that Vidya is soft, and innocent, but she is very strong on the inside. Her heart is big, but her love for her husband is bigger, and for him she can take on the world...
Sindoora is not going to know what hit her, She has always taken Vidya for granted, thinking her foolish for her sentiments, but these sentiments are going to fall hard on Sindoora. She has underestimated the love Vidya has for Saagar, and the strength of Vidya.