Erya
It should not be too hard if she is Filipina.
My wife is Filipina and worked previously in HK, she would know more about this than me, but from what I know -
You will likely just need to re-employ her under the HK domestic helper standard employment contract. Once she has that she can get an employment visa easily enough, and you are sorted.
When are you are going there? (we are going back there ourselves to live and work in August!)
If you have time, and want to sort out the paperwork in advance of travel then you might give Lloyden a call. They are a small immigration specialist company, run by an ex- HK immigration official. I don't have a number to hand, but their address is 28 Lockhart Road, Wanchai HK.
They did some work for me before and were okay. However they will charge a fee naturally and give you proper professional advice. Though I recall I had to do most of the form filling and running around myself!
Another option here in SG would be call to Lucky Plaza on Orchard Road - there are a variety of specialist maid recruitment agencies up stairs, some of which specialize in placing maids in HK. Why not start with them?
In any case you can likely do it cheaper, if not for free, yourself after you get there. The paperwork is not too complicated, providing you already have your own employment visa and HKID card in place already.
Filipinos get 2 weeks automatic tourist stamp on arrival in HK. She might however need to exit HK while the paperwork is processed.
There is a right Filipino maid 'mafia' in HK, and there are loads of agencies that can help you and her get sorted up in HK. Most are located in Worldwide House in Central, which is like a small suburb of Manila - full of PP shops, restaurants, and shipping services.
Sorry bit of a rambling response, but I think I have covered some of your options.
Regards
Julian