Thanks again to Maneesh Dube for sending me this puzzle. Many people responded to this, however only a few got back to me with a complete answer. The ones who answered completely are Vikas Jangra and Ruchir Godura. Many others, including Maneesh himself gave only a partial answer.
The trivial answer is twice the speed. However, there are an infinite number of answers. Maneesh’s speed can be 2 times, 3/2 times, 4/3 times, …. (n+1)/n times faster than Nandini to meet at the same point. Complete solution on this link:
Hope you enjoyed the puzzle!