Last minute things do come up on rare occasion. What would you want the girl to do in that case?

I would reach out to Roxanne Heart. TER # 273316.
She is the best at what she does.  
 

You can surely find multiple candidates in the age range you seek in that time.  As for guarantees, this is the hobby...noting is guaranteed until you pass through the door!  You can only do your research, and minimize the odds.  You have enough time, though.

A dinner date sounds delightful and can be guaranteed with a deposit.