This is real nubie question but here goes. If the donation is X and the incall is at a hotel of her (or the service's) choice, is the cost of the hotel on top of the donation or is it included?

It would be included, unless you had arranged for her to book a room just for you to visit.

IN call location.  "You go to her."  She's responsible for the room.

OUT call location.  She goes to you.  Where ever you may be.  Home.  Hotel.  Where ever.

Exception.  She does not have an IN call.  You do not have an OUT call available.  You do not want to rent a room in your name.  You get her to rent the room & you reimburse her.  

IF you rent a room in your name, you should not leave her in possesion of it, even if you pay cash.  You'll have to show a crdit card as a guarentee.  Anything that goes on there...  damages, mini-bar, a party, LE arrests for something...  gets linked to you.  
skb

And book a hotel that is convenient to you, the cost of the hotel is built in.

I had a client ask to see me downtown, although my incall is in the burbs.  He, for obvious reasons, could not host.  In this case I let him know that the cost of the hotel would be added to my donation and he readily agreed.  It saved him from having to drive and hour or more (one way) to see me.

Thanks gang. I really appreciate the guidance.
See you around.