Not defending Suman here but I feel after the Yatra outburst Suman is playing a game, although dangerous one (me definitely not liking it) to test Shivi's relationship to see whether they can respect each other and stay in this marriage or not.
We all know how Shivi insulted and disrespected each other in public and when they came home after the fight and Suman said 'if you can't stay with each other with respect then separate and neither Shiva or Raavi protested.
Raavi then came back for Dhara and seeing how she is managing household well and probably also has seen something in Raavi's behaviour (I can only put it down to her experience) that maybe she is right for her Shiva and knowing how Dobi Raavi is and not going to speak up and neither will Shiva so by bringing in Dasha might trigger Raavi because she knows Shiva won't budge. A. because Shiva is her son and he can do nothing wrong and B. family tried pacifying Shiva but no result so bring this 3rd angle route.
Again, I am not defending Suman here but trying to see her perspective but if makers have decided to damage her character too then I am all wrong.