Seeallsides:
The “mentioner” in your case has a legit expectation for 1/3 of standard shadchnus. He was the person who suggested it and based on your despription the boy and girls were ready to proceed and used a new person to serve as the go between.
No reason for someone to feel weird aobut paying money that has been owed for years. It probably feels much weirder to come back as a gilgul becaue they didn’t.