Some people think that she would be happy that he is rich and would be a catalyst in SidNi reunion. But I have a strong feeling that she would hate Sid. B'coz as far as DD's character has been shown, she always hate people who cheat. Be it her husband, or Bablu ( during Pratima track, b'coz he hid it from DD).
So I think she would be angry with Sid for cheating Roshni and being a reason for her sadness. And when Roshni would want Sid out of her life, DD would fully support Roshni. Thoughts??