I will not blame Jagya that he told half truth. He confessed that he did wrong and that is a great thing in itself. It is upto mannu to accept it at face value.
But why did he hush up about gauri? The reason for his breakup was Gauri, not Ganga. Mannu may think that ganga was responsible for the breakup.
About ratan. This was the right time for Jagya to tell about ratan too, not fearing ganga. Jagya could have told what a sub human ratan was and mannu would have turned out another ratan. Ratan might have saved mannu's life but he did not do it voluntarily.
And dadisa should have been there during these revelations and she should have told that she is no devta but did lots of mistakes like bal vivah, not allowing anandi education etc.
Here only 2 persons come out completely clean. Anandi and Ganga.