Sita, I checked with a panditji here about this. Though he mentioned that this was a highly unusual situation, the rules of North Indian vedic marriage stipulates the following:
1. The ring must belong to and must be procured by the prospective bridegroom.
2. The prospective bridegroom must ensure that the ring is fully inserted in the ring finger of the prospective bride till it reaches the base of the ring finger.
Now regarding the first point I am told by the forum here that Manav's original ring was changed and the ring used was Mohan's. Regarding the second point, the video clearly shows that Manav struggles to get the ring halfway through - its Mohan who pushes in the last bit so that it snugly fits at the base of Megha's finger.
Therefore on both counts, it appears that Megha has actually got engaged to Mohan. What a man, Mohan Bhatnagar !! Got engaged to his sweetheart in front of everyone without anyone even getting to know! No wonder he was happily distributing sweets to celebrate his engagement with his Mirchi Madam.