Final answer:
The ethical principle being violated is integrity, as altering the financial statements to improve the company's image goes against the principle of honesty and truthfulness.
Step-by-step explanation:
The ethical principle being violated in this scenario is Integrity. Integrity refers to being honest and truthful, and altering the financial statements to improve the company's image goes against this principle. By misrepresenting the actual data, the management accountant is compromising the integrity of the financial statements.