Some Samsung phones have dual messenger settings that allows two accounts on the phone at the same time.
This is found under Settings and Advanced Settings and Dual Messenger.
I'm wondering if she or you have inadvertently set this up.
In regards to YouTube are you both using the same login or email etc ?
Daily Driver > Samsung Galaxy s²⁴ Ultra 512Gb ~ Titanium Black.
The advice I offer is my own and does not represent Samsung’s position.
I'm here to help. " This is the way. "
