Lori - There are multiple good reasons for your sister to be there. I had a lumpectomy a year ago for Stage II breast cancer with micro-metastases to the lymph nodes and no (supportive) family in the area. I have a very close network of good friends (that birthday dinner group a week ago) and I carefully scrutinized each of them for stability, availability, and attention to detail, settled on one and asked her to go with me to ALL my appointments as my advocate. Best thing I could have done as the initial diagnosis conflicted with what they learned later and the treatment plan changed midstream, etc, etc. Having Stacy there with me every step of the way was so reassuring because when I missed something or didn't understand, she did, and vice versa. She took copious notes at each appointment too, so we could sit down and debrief afterwards. That also turned out to be essential to the way I process information and make decisions.
Hugs to Barbara for realizing something you need and stepping in to fill that need. Thank her for all of us!