Apple Watch Activation/Pairing

My sister got an apple watch for Christmas this year, and while trying to pair it, the prompt asks her to connect to an old Apple ID. For backstory, she is still under my moms family plan in terms of payments, but she has her own Apple ID for app downloads, music, etc. & has not had an issue switching phones with her personal id as well.

The issue is that when she goes to pair the new watch, it goes and asks her to pair w the my moms old Apple ID, to which she has lost the password. we have tried putting in the information, hitting forgot password, waiting for support, you name it - kind of hoping there is a way to override which Apple ID is being used? If anyone has any information you'd be a lifesaver!