How do I change the "Owner" of my iPad?

When I bought an iPad for another family member last year, they didn't have any Apple account, so I set it up under my Apple account. I have an iPhone and Mac desktop as well. So that worked OK for a while but when they message, etc, it shows under my account, even though we set her up with her own Apple ID a while ago. Now after some OS and iOS upgrades, when my iPhone receives a telephone call, the iPad rings as well. Yes, it rings like i is getting a call. The iPhone will be sitting next to it and both are ringing. The devices are all doing iCloud sharing, but maybe not set upt the best way.

If there is an easy fix without switching ownership of the iPad to the other family member, I am open to that, but maybe it is better to just split it off and assign the iPad to her completely, if that can be done.

Any help apperciated.