I don't think you can get a China visa for the Indonesia maid, the procedures are complex, you can try to apply for China Tourist Visa (L) for the maid, prepare the required documents: her passport, one filled visa application form, one recent passport photo, the work contract. Your daughter, her child, the Indonesia maid and you can apply for visa at the same time to enhance the chance of sucess.

Her Singaporean husband has to send you all an invitation letter, the copy of his passport, China work permit and residence permit. The marriage license and birth certificate should be authenticated by China embassy/consulate in Indonesia. You'd better find a travel/visa agency to do it for you, the procedures are complex and time consuming because your situation is complex.