I'm seeing a lot of people who feel this is too rushed and unrealistic. Sadly people can turn on others quite suddenly even with only small bits of doubt spread around. All the more if you're new in a place. If they are told by someone they believe have more authority or knowledge, or that they consider more trustworthy than the accused, they can easily be convinced. In this case the mayor of a small town gets told by people from a bigger town and who look respectable and with ratified backgrounds that someone has a past and are untrustworthy, he mixes that in with words from the villagers that the new lady healer uses unfamiliar magic and he feels like there's enough to doubt there to ban her, all the more since the village will lose nothing since they now have a new healer.
And once the supposedly trusted mayor shows his trust in the new healer and expresses doubt in the old one, that's all most other people need to stay away.
It doesn't help that she is hiding things like where she comes from, and who she is. Even if she's trying to help, people would pick up that something about that group is fishy, and now they've had it confirmed as "fishy bad" not "fishy of no consequence".