The balance, settled at the door when she arrives
The balance is the half of the fee that was not paid ahead. It is settled at the door when she arrives, in euro or in another major currency by agreement.
Where a booking carries a deposit, the deposit is half the fee and the balance is the other half. At an airport room, which always carries a deposit, the balance is what remains to be settled when she arrives. Whether the booking was one hour or a full night of eight, the sum at the door matches the sum that went ahead, no more and no less.
When it is settled
At the door, at the start of the visit, before the session begins. Settling it then means nothing about money is left for the end of the evening, when a traveller who landed late is ready for sleep and nothing else.
In what currency
Every figure on this site is a euro figure, and the balance is settled in euro as a rule. A traveller who has just arrived and still carries notes from home may settle the balance in cash in another major currency, provided the exact sum in that currency is agreed in writing in the thread before she sets out. The thread confirms the figure so that nobody has to work out an exchange rate at the door.
A booking with no deposit
Someone the house has looked after before, booking an hour or two for later the same day in a city room, pays the full figure at the door rather than half. That case never arises at the airport, where half always goes ahead.
Nothing added
The balance is the balance: prices include all taxes, and nothing is added at the door for the hour of the night, the journey or the distance. If a session is closed early, whether by you or by your therapist, the fee for the time reserved stays due and nothing is charged beyond it. The deposit entry covers the first half, and the cancellation policy covers what happens when plans change.