You can delete your comment, but you cant trust that she hasn't taken a screen shot of it. You could delete her as friend (but then she would find out and maybe even more mad) or block her from seeing your posts, but keep her as a friend, as well, and make your account more private if you havent already done so. I wouldnt trust her one bit. Her argument is weak too, you didn't say anything discriminatory about any specific religion. Plus schools have WAY too much to deal with right now than this.
I am in MA as well, and while I am totally with you, I feel the same way. I don't agree with the mandate at all. It will cause a lot more problems, I already have issues getting parents to bring students to get caught up on the vaccines they DO need, never mind a flu shot. Though DPH usually does flu clinics at all our city schools every year, I think parents might actually use this service this year if they do it. Usually I have about 30 students out of 400 that sign up. And you know what, I might claim religious exemption for my own children, we have never gotten flu shots and I am not about to start now, especially since they are remote.