When is her appointment ?
https://www.gov.uk/ukvi-premium-serv...an-appointmentYou want to cancel or reschedule your appointment
You can cancel or reschedule your appointment using your online UK Visa and Immigration services account.
You must:
Cancel at least 5 working days before your appointment
reschedule at least 48 hours before your appointment
You’ll be refunded the full fee for cancellations made at least 5 working days before your appointment.
You don’t need to pay the fees again if you reschedule your appointment.