After thinking it over, I came up with the following possibility: True, a match is predetermined. And yes, these two people are bound to be together. It is possible that G-d is using the Shadchan as a messenger to bring these people together. Certain people meet through other means, but G-d decided that these particular people will meet through a Shadchan’s match. So a Shadchan is a messenger of G-d who is carrying out the predetermined decree. Does this make sense to anyone?
I feel that my original post was in bad taste. I apologize.