I had similar experience as my miad refused to sign on the rules and requested to discuss with friends first.
I advised her discuss with the agency and I also send a copy to the agency. When the maid came back after holiday, she signed and returned the rules to me.
I think it's better to ask her to sign, if she refused this time, later on, you may accept she refused you more and she won't follow or respect you!
you may ask the agent to talk to her and ask her to sign. Sign a rule isn't a big deal. But the problem is she seems very mean on her personal right. Take care and good luck la.
If she doesn't sign, you can explain to her verbally with recording the voice or video. So that she can't deny in future.