While now regarded as non canon, Leon A scenario from Resident Evil 2 shows she has past form for it.So she left the gun unloaded to avoid accidentally shooting Leon. Why is there no ammo to pickup then? Because Ada wouldn't kill Leon and probably has enough knowledge of guns to know how easy it would be to accidentally pull the trigger should he not give into intimidation and fight back, something he would be likely to do. Speaking of the scene where Leon fought Ada and won by using his knife? He dropped the magazine, then Ada uses a gadget, recovers her pistol but leaves the magazine.Ada eventually applies the advice when a possessed Leon starts choking her rather than shoot Leon and risk killing him, she sticks him in the leg with a stiletto she'd been packing.
It turns out one eye didn't turn because it's a glass eye.