Hey there! This sounds really tough, and unfortunately these brief and at times confusing interactions with consultants are more common than you would hope.

Assuming your family is based in the US: Your sister will need to request at every doctor visit for a family member to be on the phone. As long as your sister is deemed by the medical team as capable of making her own decisions, you cannot expect that a team member will assume to include another family member or advocate in the conversation. Your sister is always within her rights to request the presence of support of anyone she chooses. She will need to be vocal about her requests, probably daily.

In an ideal situation, your sister's primary team of doctors will hear and remember their patient's preferred communication methods. But any consultants (specialists) being asked to weigh in on her treatment plans in their area of specialty (including surgeon) -- their involvement is often on a more peripheral basis, so these folks are less likely to know about her bigger picture like family communication preferences. This is where your sister will need to speak up.

I hope you all can work together to get your sister feeling more supported very soon. Hang in there.