Taken seriously, the fictional sentry of silencing the sentry is a real person doing something sensible. She is not standing around waiting to be a victim for our viewing pleasure. She is not a nonentity whose entire existence is a single moment. When grabbed she is genuinely startled. Should she cringe and scream she is genuinely fearful. Her feeble struggling is genuinely desperate. She feels the violence that makes her grunt, wince and groan.
An anonymous underling of villainy would not see herself as such. She may even believe the cause she serves is righteous. Conscript or volunteer she is someone with a life to live and a job to do. While on duty she guards what she was told to guard. On her own time she does her own thing and socializes with friends.
The sentry of silencing the sentry is seen differently by different characters. To her fellows she is a peer and may be an acquaintance or close friend. To her boss she is a nameless and expendable one-of-many underling. To her assailant she is a mere nuisance to be casually eliminated; deserving of her grim fate for being the foot soldier of antagonism.
As a character in a work of fiction the sentry of silencing the sentry lives to die. Her role is to suffer an inglorious doom. We are to be amused by her indignity and thrilled by the violence. She makes a name for herself as someone anonymous. Her weakness is the strength of her appeal. Her demise may prove her immortality... should her fate prove darkly sensual.