It appears as though this person hasn't hired you for your skills (her loss) but instead has hired you to be her personal software operator... the middle man between HER ideas and the sign or design. We all know these people exist. I get them every once in a while myself. They believe their ego trumps years of experience from a talented sign artists such as yourself John, and I can about guarantee you she pulls the same crap with any type of craftsman she hires.
In my opinion it isn't worth the fight. We charge accordingly for our service and I have a personal rule where I will attempt to steer the project the right way twice... and twice only. The third time that client ignores my expertise, in my mind, that proves to me that they only hired me to move the mouse pointer around on the screen for them. At this point, if I were you I would just have her come in and back seat design. It sucks, but it beats the endless back and forth with a know-it-all. It sounds as though that is what she was expecting and is what she wants. It's her loss. Take her money, finish up the project her way and move on, or as Chef Ramsay says: "shut it down". It's your call.