The second half of the fee, paid on arrival
The balance is the half of the fee not paid ahead, settled at the door when she arrives, in euro or in cash in another major currency confirmed in writing.
Whenever a booking carries a deposit, the other half of the fee is still outstanding when she arrives, and that half is the balance. It is paid at the door on arrival, before the session starts, so that nothing about money is left to the end of the visit.
Paying it as a visitor
All figures are in euro and include all taxes. A visitor who has not yet changed money is not stuck: a balance paid in cash in another major currency is accepted, and the exact sum in that currency is confirmed to you in writing before she sets out, so there is no mental arithmetic at the door. Card, Revolut, Wise and cryptocurrency are the ways to pay the deposit; the balance is settled on arrival.
How the two halves fall
Whatever the length, the door takes the same share the deposit took. A ninety minute evening leaves half the ninety minute rate to hand over, a two hour visit half the two hour rate, and an overnight half of its single sum. The one booking with no deposit, a returning client's same-day hour or two at a city address, is paid in full on arrival.
Having it ready
Put the balance in an envelope or a separate pocket before she arrives. It saves a search through luggage and keeps the first minutes of the visit calm.