You may refer your helper to www.labour.gov.hk/eng/faq/cap57I_whole.htm
Q4. Can an employer make payment to an employee in lieu of annual leave?
A4. An employer should not include in an employment contract a term to forego all or any of his employee's annual leave entitlement, including payment of wages in lieu of any annual leave days.
However, the law allows an employee to choose to accept payment in lieu of that part of his leave entitlement which exceeds 10 days.
[Example] : An employee who is entitled to 12 days' annual leave can take 10 days' leave and accept payment of the equivalent wages for the 2 days' leave.
You may simply tell your helper that, according to The Employment Ordinance, Cap. 57, the law allows an employee to choose either to accept payment or take the annual leave.
I', working in the personnel dept of my company. Yr maid is entitled to 14 days with pay. That means, you could not deduct her salary for the 6 days (last time) + 8 days (to be taken). You just pay her normal salary, let say $3320 but with no extra compensation.