HELP! Apps Linking to Incorrect Facebook Account

Whenever I go to link a new app downloaded on my phone to Facebook, or want to "log in with facebook" it brings up the incorrect facebook account, it is the account of one of my colleagues who once logged in through instagram as our business profile is linked there. Now every app wants to log into her facebook, its driving me nuts, im not logged into this account anywhere else I dont even know the password but I cant change it to my own, PLEASE HELP!