Fynn, your story is so true. This past Halloween we had several of the horrible, elaborate rubber masks we were goofing around with, and my son and I put some on (a devil and a werewolf). Liesl freaked when she saw us. She was confused by the fact that it looked and sounded like Dad and big brother, but clearly the mask was disturbing to her. Once we took them off--friends again.
On a recent walk at the local school on a rainy morning she was again put-off by all of the umbrellas and hooded jackets. She definitely notices when people don't look like "normal" people.
For the OP: please don't forget to slowly and gently introduce your dog to such odd items as strollers, scooters, backpacks, hoodies, umbrellas, walking canes, walkers, etc. Let your dog siff these when they are still and unoccupied, then move them gently until she realizes that is no big deal, then use them yourself so her trust of you transfers to them. You can desensitize your dog to these things that a shy dog finds so scary.
Liesl, b. 1/1/11