Hey there, Mafalda20.
Welcome to the Apple Support Communities. It sounds like you have some questions about your Apple ID and your daughters Apple ID. We know that keeping your data private is vital, so we can understand your concern.
It’s not possible to merge Apple ID’s. If you’re seeing each other’s info, you must be logged into the incorrect account somewhere. Learn about the places you can sign in with your Apple ID: Sign in with your Apple ID - Apple Support
Then check each place on both of your devices to see if either of you are signed into the wrong account.
Don’t hesitate to reach back out if you have further questions.
All the best.