I hope your mom will be OK, Artie. The thing with the boosters is that they generally don't protect against actual infection itself for very long (I think the most recent one is supposed to be effect against getting infected maybe for a few months at best?) But they are supposed to be quite effective (for a long stretch of time) against cases becoming severe enough to lead to hospitalization (or worse). So hopefully, the booster will help protect your mom in that way, and the antiviral will also help.

In the beginning, the first couple doses *were* more protective against catching it. But then more contagious (but less dangerous) mutations, mainly omicron, developed.l

At least, that's how I understand it from assorted articles I've read. Note that it doesn't make the boosters useless. They just don't do what many think they do (and there's a really low percentage uptake on the most recent one and pretty low on last year's bivalent one, too, so less protection in the general public).