I think MT (mataramji) is basically a "nice" person.
Although MT is shown to be tough and punishes the people who "do not tell the truth", I think she will actually turn out to be the one who will unravel the truth of Abhay being Dev. MT is shown to favor the truth--and when she will realize that Abhay is Dev, she will help RaDev. She already is suspicious about things and does not trust her kids--however exactly how the story will unfold I have no idea. It may be that Vibha will come forth and talk to MT or there will be a show down and Abhay/Dev will regain his memory and will tell MT.