Final answer:
The reference text provided does not match 'The Glass Castle' by Jeannette Walls, and thus, the question about Erma's sandwich for Jeannette cannot be answered accurately. Please provide the correct excerpt or clarify the question.
Step-by-step explanation:
The question refers to a moment from the book 'The Glass Castle' by Jeannette Walls, a memoir detailing the author's childhood experiences.
However, the provided reference text does not match the scenario from 'The Glass Castle'; it seems to be from an entirely different narrative and does not mention Erma or the type of sandwich sent for Jeannette's lunch on the first day of school in Welch. Therefore, based on the information provided, it is not possible to give an accurate answer to this question. If you're looking for information on 'The Glass Castle', feel free to rephrase or provide the correct text excerpt.