。
She was fully guaranteed her freedom.
Literal
She [topic-は] freedom [object-を] completely guaranteed-was.
自由を保障された (was guaranteed freedom) uses the passive of 保障する (to guarantee/ensure). 完全に (completely/fully) emphasizes that the guarantee was total. The passive makes her the recipient of the guarantee — someone or some authority gave her this assurance. 保障 and 保証 are homophones with different nuances: 保障 is for rights/security, 保証 is for warranties/pledges.