Re: What Would You Do in This Scenario?
Personally, I don't borrow or loan money. If someone asks for a loan, I ask how much and why. I decline if the loan is more than im willing to give them. I give the cash without strings if I want. This has preserved relationships even when the person expected to lose their house.
I would not accept the agent unilaterally deducting any amount. At the same time, I would write a check for the entire commission toward repayment of the loan. The commission is money you wouldn't have at all had it not been for the other agent. You were already compensated up front by the other agent and apparently spent the commission. Get this loan out of your life.
As a practical matter the other agent now has a primary relationship with the client and doesn't need you. The best approach is for both to keep their word and go get some more business together. I'll split any case you want to bring me especially if it is business I couldn't have gotten my myself.
Commission is only money and not worth losing a friend over.