Idea was not to show Alekh is mad ,Idea was to show the girl what is the condition of the person she has come to see,the point is that the girl should know everything about Alekh if she is going to marry her,Vasu would never tell directly that Alekh's mind is like a child's Mind,She said he is in shock because of sadhana's Death.
Vasu would Never Let anyone tell the truth to the girl or her parents,so this plan
@bold : Vasu did tell the match-making guy everything about Alekh's condition. Its clear that she doesn't want to hide his condition from anyone. It was the responsibility of the guy to bring apt rishtas for Alekh and inform the girl's family as well (not sure about this part though).