How much time should we spend with mom during first days at assisted living?

Yesterday was mom's first day at assisted living. My sister and I were with her all day. We had lunch with her and stayed until 5:00. Her previous care giver came at 5:00 and had dinner with mom and then stayed with her until 8:00 pm. When the caregiver left, mom started to call my sister and I. She screamed at us telling us we were awful people leaving her there. She said no one was helping her to the bathroom (we know this was not true). It was an all night phone fest. Mom called my sister 6 times and me 10 times. I don't answer the phone every time she calls, but my sister does. My poor sister had a sleepless night and expects more of the same tonight. Today, my sister and I were there early, but she did have breakfast with her new table buddies this morning. Breakfast seemed to go smoothly. Sister and I intercepted her after breakfast and sat outside with her until our brother and his wife arrived. They had lunch with her and spent the afternoon going from one activity to another. By 3:00 pm they tried to leave but mom was in the throws of a major panic attack guilting my brother into staying. My sister had to go there so that my brother could leave. My sister planned to see my mother through dinner and drop her with her new caregivers at the facility to watch a movie. We both expect phone calls all night long. I wonder how we should respond to mom's panic calls. Do we not answer the phone, should we call the facility every time we are uneasy? She makes us feel like we are throwing her to the wolves. Any words of comfort or advice would be greatly appreciated. Thanks for listening.