You set them up on your QBDT, right? And, they now want to run their own payroll on QBO. Unless you can transfer from your QBDT to their QBO in less than a few minutes (I might consider up to 30 minutes FOR AN ONGOING CLIENT) charge them for it. At the very least, I would charge a new client and MAYBE offer them a discount on their 2020 tax preparation in 2021. Or, do what large companies do and give them free setup, but NOT NOW, deducted from their 3rd invoice or 12th invoice or something like that.
You could be spending your time on another new client who's not so needy. Or preparing tax returns for me through 15 October, and I'll pay!