So what? The monsters which Annabeth fought couldn't cast spells or have divine powers now, did they?
Let's say you are a skilled martial artist. No matter how skilled you are, a single bullet is still more than enough to kill you.
Get that analogy? Now I am not saying Annabeth sucks or anything. She is pretty awesome okay? What you say about her is correct to a certain extent. But let's face it, most of the time, it was Percy who was doing the actual fighting.
He pretty much made sure she never had to fight a ridiculously powerful opponent. She has tricked powerful beings before, but that's because they really were dumb, which Sadie is definitely not.
So I stand by my opinion that Sadie would win. Or if not downright victory, at least have higher chances of winning.