I hope that when Shreya visits, Sandhya gets a chance to clear things up w/ her in private. Here is how she can manage it.
Since Yuvraj & Prabha know her as Vrinda, what she can do is persuade Prabhavati to let her go out w/ Shreya in private and talk to her alone, and convince her that she's Sandhya. Yuvraj will do it no questions asked, while Prabha, who may be reminded how Vrinda saved her bacon from Sarla, will agree as well. (Sandhya can keep her new alliance w/ Sarla intact by not revealing who might have leaked it, maybe just saying it was a police plant, while warning Sarla that if she spilt the truth to Shreya, she'd tell Yuvraj that Sarla wrote that letter precisely to land Yuvraj in jail - an exposure that Sarla won't want). So both Sandhya & Sarla have each other in their power (Sandhya more than Sarla, since she now knows that Neeraj is alive, so the diary isn't as important as it just was))
So once she goes out w/ Shreya, she can privately tell her everything, but ask her to tell everyone to be discreet about it, and not to blow it to Bhosle as yet, but give her the opportunity to possess all the Jagirdar possessions and render them powerless to cook evidence. Maybe even suggest that they be in touch w/ Gayatri for all future developments. That way, the sisters will all be @ relative (tense) ease, while Sandhya doesn't have to worry about that front @ all.
Once she comes back and shows that she's convinced Shreya, it will also help her get Prabhavati in her grasp, as she so plans. One thing I fear - I hope she doesn't try to win Prabhavati's confidence by saving Damodar from Neeraj, as that could jeopardize her friendship w/ Neeraj. But if she does Damodar a favor wrt DK, Prabhavati will be more happy w/ her, while DK will remain isolated, but now w/ Sunita for company