Yeah, I'd try again tonight (maybe you'll get someone different).
If they are reputable, they should honor the price (even tho it means losing money). If she refuses, ask politely to speak to a supervisor and let them know that you'll discontinue being a loyal customer, yada yada yada. You don't have to be jerky about it, because I used to do more for nice customers than jerky ones, but they need to understand that if they advertise, they should honor (and isn't that what they pay people to do- double check and edit things so mistakes like this don't happen?).
I'm not trying to buck the system, but you NEED shoes, right??? (and if I needed them I'd be doing it right along with you).