You say recently added, how recent? if it was just a few days ago I would give it a few more to see if it settles down, if it was a few weeks ago I would take her out, Do you have somewhere else she could live, not on her own though she will need a friend.
There is a nautral pecking order to be established but sometimes they just dont fit in at all, they may pick up on the fact that she is not bright, and with thier survival insticts will see her as a disadvantadge for the flock, they may know something you dont!! If all else fails rehome her.