As a sales professional I can understand why she was like that, even though she approached you in entirely the wrong way.
Understand that pricing up your car is an administrative exercise more complicated that you appreciate. They get test pilots in all day long and really, why should they bust their tits talking PX value when you havnt even established if you like their car?!
I back up entirely their reasons for being like that, but think it's so much easier if you explain t honestly to a buyer. She handled you wrong, just try and walk a mile in their shoes before you cast them off as ungrateful.