i had similar situation with you. I belever there are many employers in HK same as you. You are not alone.
the worse is:
take a long no-pay leave
quit the job
look for a local part-time helper even the $$ is a lot
look for NGO or nursey
i would not ever let a bomb stay in my house
i also agree to have a second interview to learn more information from her, & check that whether the maid would back out from you! (sorry for just in case)