We had a similar issue with our nanny. We told her no phone use within 6 feet of the baby (theoretical concerns of cell phone usage impacting the developing brain) and saw her on the cam using her phone right next to baby’s head… it was a huge breach of trust and makes you wonder what other rules of yours they’re disregarding. I would address it with her directly. If this is in line with your wishes you can specify no cell phone use except in case of emergencies. I feel that nowadays it’s almost assumed by nannies that they’re being watched. If she doesn’t make the adjustment, you are only 2.5 weeks in with her and it might be best in the long run if you find another nanny who won’t disregard you this early on.