Yes, the empirical evidence demonstrates efficacy (and we'll assume an objective, reliable/valid measure of efficacy). However, people can (and do) choose a different course of action based on what some authority figure says, anecdotal evidence, representative heuristic, etc. There's a large fancy building (
Church of Christ, Scientist - Wikipedia) in my state capital that supports this position. It's their opinion- and one that empirical evidence would contradict- but it's supported by what they think is evidence.
Even in your mother's case, the specific example is
post hoc ergo propter hoc reasoning. There is likely a large n, placebo controlled study somewhere that supports the medication as the mechanism of action, but in individual instances it's not possible to say that it wasn't the "thoughts and prayers" that really the virus go away. That's why it's so tough to argue with/change opinions of those who subscribe to a different doninant epistemology-they just don't follow the same rules.
In deference to the OP- sorry about the slight drift in topic. It's nice to see that you are still hanging around this thread, even when you may have heard some things that are uncomfortable or don't jell with your beliefs (and despite some obvious bullying from others!)