It's your hard earned cash, this is the TA of wg's, it it were me I'd ensure she had a good review here at her prices.
I always negotiate charges, if you're chatty' lie about how many kids you have and joke, I've never had a girl refuse. They may say how very, very lucky you are, but hey it's your cash, all girls value a client, no booking is no money for her sizzle, don't forget she always keeps the sausage, only sells the sizzle.