Hindi TV Serial - Bandini - Santo finds out the truth about Birwa, and Sarang turns out to be the wrong one

What an incredible 2 episodes. Just goes to show that a serial can do anything it want, turn any character any which way, and as long as you leave some logic aside, with the script in your control, everything can be changed. In the past weeks, Sarang was in love with Monghi, and Birwa was the one who was apparently trying to stop this relationship, and in the end, she does manage to do so, getting married to Sarang just before he was to get married to Monghi - and this caused everyone to get angry, and for DM to declare a somewhat weaker link with Birwa after this.
Santu was not convinced that the marriage between Birwa and Sarang was totally real, and kept on trying to determine what was the reason for this sudden marriage, and what pressure could be on Sarang to agree to the marriage; and she openly tells Birwa that she will find out the real reason for the marriage - and in the end, by reading old stuff and by even opening Birwa's cupboard, she is able to determine some of what has happened.
What seems clear to Santu after reading older stuff is that Birwa is not what she appears to be; she has written many letters to Santu about how she is trying to ensure that she takes on the family responsibility by handling the business when DM withdrew from the family and everything; and then Santu confront Birwa about this.
And the truth comes out - Sarang knew Birwa at college, but she discovered that he was after her money, and hence she left him. He came after her, and finally discovered that she cared for Monghi, and as a result, when nothing seemed to work, she had to marry Sarang to ensure that he did not marry Monghi; even earlier, when she was strict with Monghi, it was to try and ensure that Monghi became more responsible and try to earn her living.