The degree can satisfy the credential side of the Agriculturist profession, but the position itself must be professional agronomy work. If the actual duties are predominantly sales, the application fails on the profession requirement even though the applicant is qualified.
Both halves must match: the person and the position
TN eligibility has two independent halves. The applicant must meet the profession's own credential rule — here a baccalaureate in agriculture or a closely related field — and the U.S. position must itself require and consist of that professional work.
Marguerite's degree answers the first half. The second half is answered by what she will do day to day, and that is where a territory sales role with agronomy support gets into trouble. An officer is entitled to look past the title on the letter and at the substance of the duties, and a role where advising growers is incidental to selling product is not a listed profession.
The practical fix is not to rewrite the letter creatively but to have the employer decide what the job really is. If it is an agronomy role that also involves customer contact, describe it that way; if it is a sales role, TN is the wrong category and the employer should consider whether another route exists.