Hi Brandon,
Katie is not for you! She regards you as she behaves towards you.
At present the best option for you would be to change your work place. I would not like to further discomfit you but that is your best option in your present situation. She is too old for you and if you think you're the only one in her life you're very much mistaken. If you were a bit more mature I would reccomend to you to take up an indifferent stance- that is to behave as if she was not even there! or if she was a complete stranger.
You should also disregard the friendship you assume shown towards you by the manager. He is simply being impartial.
Look for another job!