While this question cannot be answered 100% based on a short written question, since all the specific facts (your mother's condition and competency; how she moved and why; etc.) influence the answer, generally--in most cases--your mother would not be liable:1) Liability is only based on fault: e.g. acting deliberately wrongfully (such as on purpuse knocking a phone into the water) or acting in a way that is unreasonably careless (like if your mother was insisting on using her own phone or tablet in the tub and the caregiver had to quickly act to prevent it from falling in--using a phone, tablet, etc. in the tub is careless).2) Even IF your mother was at fault, if the caregiver was also at fault or careless, her own fault can negate your mother's liability: an at-fault party cannot recover compensation (like a new phone) for their own careless acts. It is careless to keep your phone in your pocket when you know you are bathing someone, since phones and water don't mix--even if you want it near, you can put it on the floor, the toilet, a chair, a counter, a shelf, etc. The caregiver's own carelessness in having her phone in her pocket at this time would be her own "contributory negligence" and should mean that your mother is not responsible.