Make a formal complaint to consulate, labour department and agency claiming that the helper never reports duty since she arrived HK and ask if the contract is effective in such circumstances. So that the relevant departments have a record and suppose they will give you a formal reply. If the labour advise you to provide the ticket subject to the contract, then you have the right to ask the helper to pay one month salary for the termination.
As I know, an employment contract will not take effect if the employee has never commenced on the agreed commencement date. Pls call labour dept to check and get their advice.
For the immigration dept, pls send letter to confim the contract is declared invalid (so as the work premit granted to the maid) as the maid has never commenced according to the contract.
If the maid contacts you again, tell her u will call the police to report her staying in HK without a right premit.
If I were you, I will ask the officer to explain and tell me according to which part of the labour law that the contract is taking effect and what is the definition of commencement. I worked in a gov't subsidary organization before. Sometimes they only give you a model answer and do not consider any other way to help you unless you push them. Even the worst case, as I mentioned, you still have the right to ask for the one month salary from the helper.
1. tell the helper to meet in labour department if she wants to get the ticket
2. buy a ticket with open date but unrefundable (it's useless for her if she is going to work in macau)
3. claim the 1 month salary in front of the officer
4. ask her to sign the acknowlegement properly