Of course, every lady will be different but I think it's a reasonable question to ask.  If you're a 'regular', I think it's good to clarify if you're "grandfathered in" with her old rate or not.  If this is the first time you're seeing her and she changed the rate *after* you booked and confirmed the appt, I think it's fair to ask.  I mean if she raised the rate enough to change whether or not you could see her for the duration of time you reserved with her, it's not fair to expect you to pay the NEW rate after you've confirmed at the old rate.

So, I would ask her but do so respectfully and tactfully.   Maybe something like, "Hi!  I can't wait until our date!  I did want to clarify something.  I noticed your rate changed, since I booked our upcoming date, and I'm not sure if you are expecting the new rate or the old rate.  I would like to avoid any awkwardness or confusion when we meet.  "

That's not the best, but I haven't thought about it very long.  lol   You get the idea.  However, make sure you phrase the question in a way that aligns with your prior communication with her so it will come off more natural.

Based on her response, you'll know if you need to adjust the appt any or cancel it, due to the rate change.

Hope that helps!  

It speaks volumes that you are paying attention to her booking website. I agree with the other poster, just ask her. No harm can come of that.