Well at first I was like 'typical' she heard part of the conversation! And now Mohini can manipulate her!BUT then it crossed my head - the line she would have heard would be 'they are asking for Parvati in exchange of Maitili'
Now knowing Paro she would have handed herself in a platter to the goons! She wouldn't have even tried calling Rudra if she knew handing herself would sort the thing! cz after all jija was in trouble 'because of her' is what she would have latched on to! She would have known Rudra was correct then, BUT she would not have at all allowed him any chances to jeopardize Maitili's safety! In other words Rudra wouldn't have known till it was too late!! She would have just walked in!!
That is very dangerous!
Today as we saw in the episode Paro is going to fight them.. BUT that is cz she doesn't know that the kidnappers wanted her n not any money! So she is blindly fighting them off to get out with all of 3 of them together!
But had she known that she was to be the ransom and had gone with Sumer on her free will, she would have first of all submitted herself! And there would be no chances at any rescue n all 3 might have gotten killed!
But here as she didn't know that there was a solution of handing herself over in exchange for Maitili she would fight!!
So for a change half knowledge would be a blessing... though no knowledge would have been the best for Paro.. but then Maitili would die..
So all in all half knowledge n what it spurned seems to be the best possible option..