If the salon owner sues Nancy, she does have a case because its Nancy's actions and statements that caused all the Nancy following trolls to leave negative fake reviews on yelp, threaten the salon owner etc. Even if she doesnt get any damage relief, it would just be embarrassing for Nancy as she is clearly in the wrong atleast in the public eye for violating both shutdown as well as mask mandates. There is no evidence to suggest this is a "set up", the owner is just airing out grievances about how influential people are able to flout laws while her salon was shut to the public for a long time.

For the owner, operating against the shutdown would mean regulatory fines or closing down her shop and that could be adjusted against a possible settlement by Nancy, as its against Nancy's interest to let this play out any further in the public.

However given the difference in influence between both I wont be surprised if the owner decides to drop everything and just move out of SF, not many can go head to head with someone as vicious as Nancy who also happens to have a lot of power