From my pov, i think passing her back the phone is fine. I can imagine myself working as a helper and far away from my family, the feeling isnt easy.. if u pass the phone to her, but telling her that u trust her to only use it during her rest hour, or when she is not doing any chores/taking care of ur child, she might feel good that u trust her with her phone. And she will feel more secure as when she misser her family, she can maybe contact them during her rest hour or at night. But do tell her that she cant use it while she is taking care the child.. and if u have a cctv in place, u can monitor her :)