I think y'all reading way too much into this, or simply missing the point.
Yeah, the likes of Ripley and Sarah Connor had to learn, yeah a lot of people in the U.S don't know how to use guns, that's all good and true, but it's not really Olivia's point. We're talking about movies, how this stuff is handled in fiction. Olivia's point is that in a movie, when it comes to a character that doesn't particularly links back to guns on a surface level like, say, a scientist, if it's a male character nobody will bother to wonder how they know to handle a gun, they just accept that he does - now if it's a female character, storytellers and studios will often feel the need to explain how she learns to handle the weapon (that if she's not completely helpless), or make her into a Lara Croft-esque heroine who's just so absurd at it that that's it - they think that the audience may not accept that she's just a woman that happens to know how to use a gun the same way they do with male characters. And she's not wrong. Nowadays less movies do that than they used to, but it's undeniable.