Anime / Manga - Nyuu With A Screwdriver

I'm gonna be honest, Elfen Lied's a bit less scary once you do the math and realize that Diclonius are only capable of deflecting weaker bullets, as everything she deflected was from either a handgun or an MP5 and every time we see a gun used successfully against a Diclonius, it's either a Desert Eagle at close range with it's muzzle velocity of 1,542 feet per second or an actual rifle, whether it be the FAMAS G2 used point-blank against one (5.56 NATO, muzzle velocity: 3,030 ft/s), an Accuracy International sniper rifle fired from a long distance and presumably chambered for 7.62 NATO (muzzle velocity: 2,790 ft/s) or an anti-materiel rifle chambered for .50 BMG (with the muzzle velocities in ft/s once again being in the high 2,000's to low 3'000's).

Meaning that they can likely only deflect fire from handguns and submachine guns, and that most rifles should be able to hit them without issue, possibly even from great distances. If this show took place in the US, Kaede would have been obliterated a truck full of rednecks with AR-15s after her first few kills and any other Diclonius that showed up would have had the police shooting scene from Akira recreated on them.

TL;DR: They could have just shot them the whole time.