I think if didi knew that Vinu is Virat’s son only, she had more reasons to not tell this to anyone. In that case Vinu wont be an orphan anymore, and Virat wouldn’t have to adopt his own son no as he was the biological father. Then there wouldn’t have been the question of Virat Pakhi marriage also. In case they show that Pakhi knew he is real Vinu, they can show that Pakhi hid the fact just to get married to Virat.
see if vinu is the real vinu .. and pakhi knows about it ., then she will start doing some monologues immediately after Savi’s reveal ..
my only hint from this was .. pakhi was present at the orphanage..she adopted him . So Vinayak came to her by chance .. she used the opportunity to get married to virat .. they can easily show that ..
That’s why she was angry at orphanage people to reveal to sai that Vinayak is adopted..
However the creatives can play if both ways they can still keep Vinayak adopted . .. and bring the real Vinayak later on in the story