Unfortunately, you have to scale Diana for the times.
Batman has been shown taking automatic gunfire to the chest at close range without batting an eye.
Aquaman took a bullet to the head with only the slightest trickle of blood and it also didn't slow him down.
She's one of the most powerful heroes in the DCU and yet if you can take her down with a gun? It just doesn't work anymore.
Diana should be 100% bulletproof. Period. Nowadays there's Omega Beams and Heat Vision and lasers and such she can deflect/reflect, but to have every other hero in the DCU run around being bulletproof while Diana isn't just seems silly to me.
She is so powerful that the only plan Batman has is for Superman to stop her.
She has previously taken a swim in lava, flown through a hot nuclear reactor, taken a nuclear weapon at point blank range, etc.
Bullets should be so five minutes ago