Two entities recommending the same commission based product to the same people

I am running a hostel in Kenya and we recommend different activities. One of our customers could also get commission for the same product (skydiving) and claimed the commission from the skydiving company for a few people. She and we talked people into it, but we didn't know she would seek a monetary advantage out of it.
Is it completely legal and/or moral to use somebody else's platform of business to gain money when the revenue is being made from the same source. In other word, has she been stealing our customers, knowing that we established our business, we marketed to bring these people to the area, and we set up a very visible notice board that every body cannot miss displaying that activity.
Am I wrong to feel that I was fooled by that person and that we are entitled to these commissions?
If she had given them a better deal without making money, it would seem right, but isnt making money of our customers from something we could have sold unmoral?