I dont think Bimla's relationship with Mannu will extend to her interference in his love life.
Any child has more faith and trust in his parents than in other members of the family. He/she expects them to fulfil his/her demands. Mannu always went to Jagya or Ganga when he needed anything. Not to DadiSa or Anandi. DadiSa and Anandi are members of Mannu's family but he has a right over his parents to ask them for anything.He would therefore expect them to be open with him. And when he feels betrayed, they are the ones he will be most angry with.On the other hand he knows Anandi has been truthful to Shivam about his sister. Probably due to this he feels he can trust her. And SN is the only home he knows outside of BH.He cannot just run to Bimla. This is a relationship he still has to explore.