I thought it was all explained in the user manual.
When you are authenticating in Wordbooker (either for the first time or when you are clicking on the Reset) you need to make sure that the Facebook account you are authenticating is the account you want Wordbooker to link to.
Due to the way that Facebook authorisation works if you are already logged into Facebook from a browser even if you don't have a window open at the time time Wordbooker will attempt to authorise against that user.
So make sure that you are not logged into Facebook before you authorise Wordbooker. Either make sure Sharon has logged into Facebook from the current browser session or login as her when the Facebook login dialogue box comes up.
To find out who is a Facebook page admin go to the page in question as the person who created it (or as someone who is an administrator).
You should see the Admin bar at the top of the screen and one of the options is Edit Page. Click on that and then click on Admin roles....