As a fan of both characters, I hate to say Sailor Saturn doesn't stand a chance.
As has been mentioned, the real problem isn't power, at least for the manga/Crystal versions go, but the fact that these girls aren't trained fighters and have shown very few raw strength feats that would indicate they could even make a dent in him. It's also highly unlikely they could catch him off guard if he's sleeping, and their attacks aren't that wide in scope.
Plus, unlike most Dragon Ball fighters, Beerus also has access to various hax by virtue of being a God of Destruction.
That said, it'd be hard to see either of these characters actually getting into a fight. Despite her, at times, acerbic manner of speaking to the other girls, Saturn is never impolite or disrespectful to anyone about her station, and she doesn't have a big appetite, so she's very unlikely to annoy Beerus. Beerus, despite the DB fighters sometimes walking on eggshells around him, isn't usually looking for a fight and is pretty lazy about the destroyer thing. He might get a little miffed about herself calling herself a Guardian of Destruction. There'd be no fight, because they'd get along kinda-well.