Apple ID Issues

My first iPhone was handed down from a previous partner and her ID was on the phone. Several upgrades later I have my own Apple ID and password obviously. I log in to my account with my own email address and password but when I need to update an app from the store it asks me for the password for my ex partner’s email address.

I try logging out and back in but the same thing happens. How can I delete the wrong email address?

Thanks