Hi 1lovekristi,
Unfortunately if the lady is not working at the time you arrive, chances are you would be unable to request her, even for an extra fee.
The ladies have set scheduled based around other ladies and house availability.
Similar to what Flint had said, you can certainly message them or tweet them to see if they would have any objection to “extending” their stay in order to be there when you arrive, but it is up to the lady and the Madam to see if they have room for the extra stay.
Let us know if you have any other questions.
Thank you,
Client Relations