Playing devil's advocate here...
Unconditional love is truthful. There are many old sayings in India to support the exception to the rle..."tell a thousand lies to get a girl married", "telling a lie for dharma is acceptable", but there is also the saying "if you tell one lie you may have to tell a thousand more to cover up the first lie" which is the path Prats is headed on.
If anything is certain in life...it's only a matter of time...the very nature of truth is TO BE PRESENT. If it doesn't show up today it will, one way or the other, one day or the other show up. The choice is whether it shows up a person interferes with the timeline ...meddling in destiny of another person even if it's only one's spouse has it's consequences.
If you go back to the time Prats hid the truth about her kidnapping ...she did the same thing...she followed as her Papa Shamu led her to believe that Krishna would never understand the kidnapping and he would explode. Krishna shut her out and she banked on his love for her and got through the tough times. But she hasn't learned a thing from it.
Whatever Prats's justification (to protect him from public ridicule and devastation), there is always the risk that her crying and sulking is going to get him to act out of desperation. He may march up to the docwa and demand a way to fix the problem and hear it straight from the docwa's lips that he's the one with the problem. How is Prats going to save him from getting devastated then? What happens if he goes ballistic or goes AWOL after hearing it...while she's locked up at the Niwas? Either way Krishna is going to be devastated... at least telling him and being there for him and working through it as a couple would be a far better choice. She may get Arushi to promise to hide the truth. What's not to say Naiki won't go snooping and find docwa and get her to spill the truth to her? Nasty naiki will have a field day with it and rejoice in the fallout.
Prats has made a poor call esp. in such a sensitive, personal matter such as this. She has exposed Krishna to the risk of being humiliated in public by her silence.