Final answer:
If it were discovered that the letters belong to the protagonist, her autonomous pursuit of knowledge could be threatened, as others in authority have already shown a desire to control and limit her access to learning.
Step-by-step explanation:
The passages provided suggest a narrative where the protagonist has gained some form of knowledge or skill, which others (such as a 'mistress' or 'she') do not want to be discovered. The first passage implies a secretive attainment of skill, perhaps in literacy or some other form of communication denoted by 'patterns,' and an individual's determination to keep this knowledge private. The recurring message that 'no precaution could prevent me from taking the ell' indicates a pursuit of knowledge beyond the initial allowance ('the inch').
In the context of the interactions described in the last passage, one character feels possessive and certain of another's attachment, embodying a dynamic of control and expectation in their relationship. These narratives speak to themes of empowerment, the acquisition of knowledge, and personal agency in the face of control.
If this knowledge—likely represented by the letters or patterns—is revealed to belong to her, it's implied that her autonomy and secret empowerment could be threatened. We can infer that exposure might lead to a crackdown on her ability to learn and evolve, already hinted by the scrutiny described ('I was most narrowly watched').