she may have scented something on those people(other dog?) who knows...don't let it get to you. At her age, she may be growing into her independent mature self and not really care for strangers to approach her. If she had made the first move towards them, it may have played out differently. She knows training is structured and she has to stand for exam, but on a hike, on a line, in a down, then a sit, she may have felt vulnerable.
It may be too personal, but hospice is for who? You don't have to answer. Maybe she is sensing some angst with your emotions right now too. Just a thought....