This happened to us as well. Our helper's performance had been mediocre at best depsite having worked in HK for 10 years and prior to that in Singapore for 8 years. Her cleaning was good, cooking inconsistent and during her time with us she constantly made demands for more compensation/benefits/time off (even though we give her bonuses and go away at least 5 weeks per year) and frequently gave bizarre and inconsistent stories.
While she couldn't get kids to eat right or do their home work no matter how much we pleaded (both my spouse and I work full time and long hours), the kids do love her.
Anyway all parties signed the new contract last month and it was processed through the Philippine Consulate (and we believe the HK Immigration as well since she never made it clear to us whether that happened or not). Our helper then text messaged us 4 days before the old contract ended that she quit and would no longer honour the new contract.
Beyond scrambling to find a replacement, we were more concerned about the possiblity of her getting a new visa under the new contract so that she can work on part time, live out jobs illegally for more money (not sure if we are just being paranoid or if this indeed can be a loop hole for the helpers?).
We read on the HK Immigration website that failing to notify Immi in the event of contract termination the employers can be fined $50,000 and subject to up to 2 years imprisonment. Needless to say we immediately sent a withdrawal letter for the new contract application to HK Immigration and copying Philippines Consulate.
In retrospect we should have accompanied her along the renewal process. I suppose just another lesson learned the hard way. By the way, she also filed claims with the Philippines Consulate stating that we owe her airfare, allowances and annual leave until we showed her all receipts signed by herself and credit card, itinerary and the travel stamps in her passport to prove otherwise.
We then had her sign a letter agreeing that she would not make further frivolous claims against us. Indeed unfortunate that it had to end this way.