The article is a bit unclear whether a test was adequate, but if it was, an anti-testing stance would be completely bizarre. Have the anti-vaxxers said that they won't get tested? I hadn't heard that.
My reading of the articles about the protocols approved by Actors Equity is that, unless the actor has a medical reason, a Broadway producer is allowed to say that you must be vaccinated if you want a Broadway job. So she's not just losing this job, she's losing any possibility of appearing in a Broadway show until she gets vaccinated. It reminds me of nurses or other health care providers who are getting fired because their hospital wants all of its employees to be vaccinated -- is there another hospital who's going to hire someone who got fired for that reason?