Will you still be the person who is managing your listing and screening guests? If so, then I would just pay the regular cleaning fee, and then a separate fee for the trips she will have to take to welcome guests and do key exchange.
If she is going to be managing the entire account and your listing, keeping up with Airbnb site changes, local regulation, and reading this forum to keep abreast of how to resolve issues with guests and customer service responses, then I would pay a percentage like she is the property manager. But still pay her a separate cleaning fee.
In some areas in the U.S. only a legal real estate broker can be paid commission to manage a property. But you are allowd to pay someone hourly to manage it.