You need to compensate her something for her time. Tipsy or not she still took time out of her day to see YOU. Knowing this is a P4P thing, not compensating her 30-40% of her rate (or so) would be very bad form.
Besides, how do you think she would feel, coming to you in good faith and trust, then you reject her.
Because you asked the question at all I'm going to assume you work extremely hard for your money and you can't afford it to go to just anyone. (rightly so) Meeting a provider in advance of BCD is a widely used tactic to weed out the providers you just don't like. Being a consumer I can understand your position... being a business woman, I can't imagine meeting in advance. We have reviews and information on us out here to aid you in your choice.
To sum up... Pay her SOMETHING. Don't be a jerk. Do your research and create an amazing time... You are actually part of the equation (even though a GREAT provider can swing it alone.)
Now if we are talking about the girls that charge 1000 and up, well ok I can understand meeting first. You still have to give her something for showing up. I mean... she SHOWED. WOW!!!! Gotta reward that just a tad.
OK I have had some incredible Mead tonight so this is my version of PWI. I'll look tomorrow and see if it came across as well as I hope.
OH and Edit: If we are talking about the guy being too tipsy it becomes a question of safety. Regular rules don't apply. It is over ridden by the "Oh shit, why did I leave the house and how can I get back there as fast as possible" rule.