Why fire over the wall when (depending on the round) the wall just adds to the damage to the enemies, removes potential tactical footholds/defendable positions, and you have a new opening to go through to wage more chaos.
@hashire-sori-yo while i do agree, the simplicity of the revolver drum design allows it an ease of manufacture that can easiest be seen in how early it became massproduced on a scale comparable to single-shots
3km would be almost two miles for those of us who use the shitty imperial system... And considering how far off the shots were from the person sized target I'm pretty sure it'd be fine even without the added accuracy when she's aiming at a dragon... and if she's using that on humans that's just overkill