You're a thoughtful guy.

I would love to be asked prior to a meeting,that way we can pace ourselves accordingly to fullfill your request,xxx

You are paying for her time (and companionship only, of course not per pop so I think it's very unfair of the provider to think the session is over after one time.  But, asking up front is a good idea if you have any doubts if multiple pops is on offer.

It is polite to ask first, but if she says no, go elsewhere.
I think it is your right to ask for a second cup.  You are paying for time, and if you can do it again in that alotted time, go for it!