Were it up to Bella, I think she would have asserted that one pet sitter was plenty. But for various human reasons, she had to contend with two! She quickly made her preference known by refusing several walks; first by ducking back into her room when she realized her next walker was even less familiar, and then by refusing to move from her bed at all. Treats were still acceptable, but not from this second person's hand - only if laid in front of her. This went on all day until pet sitter #1 returned.
Several days later, we tried again. This time Bella came after just a few attempts. She walked with me almost comfortably until she decided it was time to turn around, at which point she crossed the street like it was her mission, pulling me along swiftly. For a moment I forgot who was in charge. We made it back to the house just fine, but her tail began to tuck as we got closer. She knew exactly where she was, but she seemed nervous to enter the house, and nervous about remaining where she was, as if once again there was no safe place for her. Eventually she walked through the door and scurried back to her room, anxiety in full force.
The following day when I called her (both pet sitters present), she seemed much more certain about what to do. She glanced back at her bed, but then trotted down the hall with encouragement. We (Bella included, I think) all felt relief! A walk with Valerie (pet sitter #1) was her reward for coming willingly.
All in all, I would say Bella did very well with this confusing modification to her company and routine. It seems that her fear about what could happen still trumps what is actually happening, as if something bad or scary is always just around the corner. But to go from coming out for one person to coming out for three people is 200% improvement, and who wouldn't celebrate that?! I trust that if we keep at it, Bella will continue to get more comfortable, and to know some people as kind and trustworthy. For Bella - just like the rest of us - to recognize what is, instead of looking for what we fear (or what we wish), is one of the hardest tasks of all.