Chances are that if she's 60, she's been there a long time and is anxious to pension out. Perhaps she views your position as her assistant, so maybe you should clarify with someone above her to find out if this is so.
Whenever I've had someone above me treat me with disrespect, I straighten them out very quickly. I simply let him/her know that although I'm not the same paygrade or of the same authority, I abide by the same rules and use the same toilet.
That being said, two can play her game. You could always use that extra half hour of lunch as ammo. (Did I really say that? )