Final answer:
Gerda's sense that she will never see Arthur again, after receiving his frayed, dirty letter, likely results from the condition of the letter symbolizing hardship or finality within the narrative context.
Step-by-step explanation:
The question pertains to a character's sense of foreboding or a premonition of loss after receiving a particular letter. Given the references to various narrative texts where characters react to letters, it seems the core of the question is a thematic element found in literature, where a letter symbolizes a pivotal emotional or narrative moment.
Gerda's realization in this context likely stems from the letter's condition - being frayed and dirty, which might symbolize the adversity faced by Arthur, as well as the emotional distance or a finality that the state of the letter represents. This condition of the letter, coupled with the context within the narrative, may suggest to Gerda that Arthur has undergone a significant hardship, possibly even death, leading to her believing she will never see him again.