She is prescribing a medication for an, as yet, unproven off label use to a family member who is not her patient - that's a medical ethics no-no. Yes, I am assuming her husband is not her patient because that's another medical ethics no-no. So, from a medical ethics point of view, she cannot be correct and there is no "what if", her actions are wrong.
So far the studies are not showing ivermectin to be more useful than vaccines. When you just look at potential side effects, ivermectin is much worse than a vaccine. One of the known side effects, rare but known, is temporary blindness. It's a known side effect. Temporary blindness. Ethical physicians do not give medications that might cause temporary blindness for unproven off label uses to family members, they just don't.