It's legal to give money to the maid for buying the air ticket themselves, provided that you ask her to acknowledge receipt of the money.
However, you should check with the travel agents for the cheapest airfare provided that the departure date is changable within 14 days of termination. So you can give you that amount and advise her to issue ticket from that travel agent.
如果你問過旅行社都係咁上下, 咁比現金都無問題, 但一定要寫定張收據, 錢碼註明HKD2,300.00 in lieu of air ticket. 以下係工人完約時需要簽的收據:
Receipt for Payments upon Expiry of Contract
I, XXX XXX XXX (name of employee), I.D. / Passport No. XXXXXX, receive the following payments from my employer XXX XXX XXX on ___________(date) *in cash / by cheque / by bank autopay.
1. Wages (from ______ to ____) HK$ xxx
inclusive of payment for the following:
(a)statutory holiday(s) (date(s):__________)
(b)annual leave (from ______ to __________)
(c)sick leave (from _______ to ___________)
(d)others (please specify) ___________________
2. Food allowance (from _____ to _____)HK$ xxx
3.Wages in lieu of notice (if any) HK$ xxx
4.Un taken annual leave pay ( ____ days) HK$ xxx
5.Long service payment / severance payment (if any)HK$ xxx
6.Food and Travelling allowance HK$ xxx
7.Payment in lieu of air-ticket HK$ xxx /
return air-ticket of ____________ (Airline)
8.Others (a) ____________ HK$ xxx
(b) ___________ HK$ xxx