Never sign in with a different Apple ID unless you know fully what you are doing. Apple has now merged all her data with yours and you now get to enjoy spending a day sorting through it all piece by piece to get rid of the stuff you do not want. To start with, get her to get her own Apple ID. Change your password so she can't sign into your account again.
Send her this link:
Click here to see how to 'Create an Apple ID'. --> https://support.apple.com/HT204316
Go to the Apple ID website https://appleid.apple.com/, then sign in to change your Apple ID or password.
What to do after [or before] you change your Apple ID email address or password - https://support.apple.com/HT204071 - "After you change your Apple ID email address or password, you might need to update your sign-in information with any Apple services you're using." - Or if you're seeing persistent disabled messages or repeated requests for the password to your previous AppleID.