Ze is trots op haar werk. (She is proud of her work.)
trots takes "op" (trots op = proud of). Example: Ze is trots op haar werk. (She is proud of her work.)
Ze is trots op haar werk. — She is proud of her work. The preposition op is fixed, so it doesn't change with the sentence.
Fixed prepositions come up all over the A2 exam. The platform drills them in real exam tasks, AI-graded across all five DUO sections.