Interesting disscouision here.
What I think is that mystery person was not planned as a part of postleap and is there as backup plan. CV's are running out with ideas about Hyar. Selling brides, organ trafficking, elections, Chakor's kidnapping... What is next?
There are possibilities that mysterious person was kept so Sukor both or one of them can be blackmailed by Imli. Most probably.
But there is possibility that person is HyAr's, concretely Imlis weakness. Why do I think like this? Chakor will soon send Chagan and Pakhi to spy. Means most probably they will soon find out about captive person. Elections didnt started in full form yet. If intention was to blackmail Chakor then it would not be revealed before elections are on its peak so Chakor can be blackmailed in last moment. To add on this if person is kept just for blackmailing then why would Hyar give her food from their hands and why would Imli be so worried.
If its Tejaswini then I doubt she will belive Suraj is keeping her there. She will know about his memory loss or she will think he is dead. To add on this, I know they showed only two scenes with mysterious woman but why Suraj like Hyars most loyal slave was not there with them? Question is does Suraj even know about that place and that there is some person. What in this moment sounds most logical to me is that Tejaswini don't know about Hyar, she believes RV is taking her captive, Suraj is not there (memory loss or he is dead) so she trusts only that Imli can save her.
However, whatever possibility comes on my mind one thing just doesn't fit in it and that is Hyenas behaviour.