I think that even if the truth is revealed, it is not anandi's place to do it.
If alok and meenu, her elders, have seen it fit to keep it a secret all these years, then she must respect their reasons. Or put pressure on them to tell the truth after all these years. But she should herself not stick her chest out and be the paragon of virtue and moral integrity.
In american tv serials, there are indeed stories like this of hidden adoption or baby swaps/baby exchanges - but they are only brought out in the open because the child needs a bone marrow transplant and the doctors will do some genetic testing or something and find that the parents are not the biological parents... so then the hiders feel the need to bring out the truth before the doctors come out with their results.