30 appointments can't separate a deck effect from noise. At 12 of 30 you're at 40%, and the standard error on that proportion is about 9 points, so her true rate sits somewhere in the low twenties to high fifties. Detecting a real move from 40% to 50% takes a few hundred appointments. Anything she reports back to you inside a year is the mix of her lead sources changing, since referral appointments convert far above portal-lead appointments and a couple of extra referrals swamps everything you did.
So measure things she can see happening. Turnaround from her call to delivered materials. Whether the seller signs at the appointment or asks for a week. Whether her list price holds or gets cut in the first 30 days. Whether sellers come back to her. Those are process facts, and you can price against delivery and turnaround rather than against wins.
The risk you're circling is real and the fix is contractual. Write the scope as deliverables per appointment with a fixed revision count, and say plainly in the first conversation that materials support a pitch she gives. If she wants outcome-based pricing, she's asking you to take commission risk without commission upside.
The thing that will actually decide the renewal is her listing count. If her appointments drop from 30 to 18, your line item gets cut regardless of quality. And post-settlement, a chunk of her lost appointments will turn on how she handles the compensation conversation with the seller. If your materials say nothing about how her fee works and what the seller is agreeing to pay, she'll lose appointments in a room where your deck was fine.
