general contractor paying finders fee?

[Michael Parks]

my dad is a licensed general contractor and found a job we bid on through a realtor. The realtor had us pay her a finders fee for finding the client for the remodel project we just did. the house we worked on has something like 12 other houses on the same lot. so yes we did pay her the finders fee for the first house.
we are going to remodel another house for the owner on that same lot. she is asking for another finders fee even though we already know the owner and paid a finders fee for the introduction. are we legally required to pay it for this next remodel on the same lot?