Child Who Never Listens

I’m a nanny of a 3.5 year old. She refuses to listen or talk to me. I’ll ask her about things at school, or give her options of what she can eat, ask her if she wants to go to the library or park and she just looks at me. One time she even said “I’m not going to answer you” 😑 I will ask her several times if she needs to go potty, I will ask her to try to go potty and she refuses. When I sit her on the potty myself, she won’t pee then second after she’s off she will pee herself. We will spend two hours in silence because she won’t answer me. I try to engage her and she just wont speak. I’ve asked her parents what to do and they said that if she’s not putting herself in danger it’s fine. I feel like it’s not fine for her development. Any ideas? I don’t feel like a good nanny if I’m just sitting in silence with her lol.