Apple Family accounts merge nightmare

I have my family members set up with Apple, however one of my daughters’ contacts are merged in with mine. More than that, if I go to look at her iCloud email account setup via iPhone Settings->Mail->Accounts-><her-email>@icloud.com (I have her account visible in my Mail app), it shows her name for the account name with my icon/picture. On that page it lists her as having all her devices and all my devices!! What begins with my icon and her Apple ID page - flips to mine unprompted. Something is very confused. I suspect it has all become to complex to unpick - what can I reset / reboot to set up her account fresh and unmerge our contacts etc.? Grateful for any help.