My Grandmother is a similar age with complex medical issues and requires a high level of care. Like you our family is dispersed and its hard when you're not there on the ground seeing whats happening. You can only do so much over the phone. A lot of the time with my Grandma she sounds quite good on the phone, mainly because she's buoyed by the phone call. So its hard to get a good indication what she's like during the day. You need someone on the ground there you can talk to you can trust to tell you whats going on. What are her care arrangements now? Is she living alone or does she have some level of assistance?

As for talking to her about it, in my experience the biggest need the elderly have is the need to feel safe and secure. While we might stress about different aspects of treatment, Grandma's biggest worry about hospital was she was not in her own bed surrounded by her own things and own routine. She finds it all very unsettling. Sometimes with bad medical news she goes into denial, and we have to work through the issues with her.

I think you're on the right track. Being patient, asking the right questions and getting informed. Keep the dialogue open with the medics, your mother and the rest of the family and work through the issues as they come up.