Communication is paramount for any relationship, particularly between husband and wife. Most serials show what happens when important things are hidden from the significant other. SR is another example.
Suman should have confided in Rajeev, not only what had happened to Tanu but also how Shalaka keep taunting her. Together they can find a solution to the problem.
It may be more difficult to confide about Prem. But then since she knows Rajeev's character by now she should not hesitate in telling about him too. She can make him understand that she did not deliberately set out to deceive him. She could remind him of the many times when she tried to tell him before the marriage but how circumstances did not allow her to. But for this she has to first confront her own feelings for Prem. Going by his behaviour lately she should realise she is better off without him.
Well if everything happens according to this we may not have a story. Maybe that is why they always show characters hiding things from each other. Personally I find it ery difficult to keep a secret. so cannot understand others who do.