Iphone 13 messing up singing in to apps

[takithes]

Hi! so, i have an iphone 13 which works just fine without any issues, except, a while ago my gf wanted to play cod mobile on my phone which requires signing in obviously, she wanted to use facebook for it, because she has played on her previous phone and had all her stuff on that account, she managed to sign in to her account on my phone, but something got messed up in the process. Now atm, any app that i try to sign in using facebook, automaticly signs in through her facebook instead of mine, even tho im signed in on my facebook app on the phone, and ive got multiple apps i'd like to sign into, but cannot, because when choosing that option, you cannot choose to write login information, it is just automatic kind of " do you give permission to do this and that blah blah". 

what could i possibly do to undo this issue?