。
She's troubled by his ignorance.
Literal
She [topic-は] his [genitive-の] ignorance [at-に] is-troubled.
困る ('to be troubled, in difficulty, at a loss') takes the source of trouble with に. The ~ている form 困っている ('is troubled') marks an ongoing state of being bothered, vexed, or stuck. 無知 ('ignorance') is built from 無 ('without') + 知 ('knowledge'). The 無- prefix is highly productive for negating Sino-Japanese roots — 無礼 ('rudeness'), 無知 ('ignorance'), 無実 ('innocence'), 無作法 ('ill-manneredness'), 無理 ('unreasonable'), 無効 ('invalid').