Just to throw out some knowledge here. Several things went wrong here, but at least some of them weren't the thought of the pharmacist. The prescription pad has something where it specifies brand only, otherwise, it is legally assumed that you can do substitutions. The doctor could have specified brand only. It is also possible the doctor made the mistake and actually didn't say substitutes were not OK, because then it would be the doctor's fault. However, if it was specified brand only, yes, that was the fault of the pharmacist.
Beyond that, this is mostly a "let's pick on the person who's easiest to yell at". Someone called it out as "just semantics" to call it equivalent, but that's a very biased way to look at it and is actually factually incorrect. Equivalency is a medical standard term for a brand to a generic comparison. So, yeah, the pharmacist would probably have been better off to explain it some more, but again, they are using the legal, medical definition. It's not just semantics. Furthermore, people seem to think that pharmacists should just magically know everything about a patient. Many things about the patient are not readily accessible to them, and there's a very small percentage chance that they had that information available. I'm sorry, but the woman was somewhat at fault here. If she had a serious allergy, she had some responsibility to volunteer that information. Advocate for yourself. People are allergic to a myriad number of things. Mention it.
On the not taking it back part, that's a store issue. Again, the pharmacist probably (not for certain but most likely) doesn't own the store. They can't issue a refund because it's store policy.
So, in all, sure, yell, scream, throw objects at the pharmacist. But just realize, the person who's being a jerk here just might be you.