Reasonably easy to transfer a maid - go to MOM's website and you can download the application form (you will need to make a new application) - allow yourself 3 weeks for it to go through. Make sure you already have you EP and tax file no.
You will also need insurance for the bond ($5K) etc. - there are heaps of posts on this. Best to do a search.
One final point - who is recommending this maid to you? If the family was American, tread carefully my friend - so many posters here have complained about maids that received glowing refs from Americans (not that I have anything against our friends across the Atlantic however, they may find it difficult to say anything bad about someone).