It's hard to answer this question without knowing the extent of your relationship over the phone with this provider.  If you have in any way discussed services over the phone, I would guess that it would be OK to ask something like "Is the donation for your time, and as many services as I may ask for within that time?".  I once had a local provider hang up on me because I asked this question the wrong way, in her opinion.  So be carful.  You may want to check her reviews here --- most of them can help to answer that question.

I would definitely say check the reviews. For me the reviews are always accurate.  I've never seen a provider and had her say "those reviews were wrong, I don't do that!".

...ask but in a nice way. Sometimes being up front with her is the only way you'll know what to expect. I'd tell you to read her detailed reviews but I have a feeling this is the only time your going to be with a Provider.

I'd bet that you'd get more mileage for your money with a local gal who knows that you'd be a regular.