Wrong email on xbox app mobile, cant change it.

Hello, recently my girlfriend made an xbox account and has been trying to login on the xbox app but running into many issues.

She originally put the wrong email in which locked thag one in. Theres no option to use a different one so she is locked on that screen with any website she uses. Anytime she trues to login to her xbox account it brings her to the same locked screen. If she presses next it asks her what characters are on her tv when her xbox account isnt linked to any xbox on the app or online on any xbox. The rest of the buttons on the screen lead her to nowhere. She cant sign in on the xbox app, minecraft, on google, etc. Shes already delted the app and reinstalled it and it does the same thing. Shes an iphone user by the way. Is there anyway to fix this?

:)