。
She gazed intently at him.
Literal
She [topic-は] him [object-を] intently gazed-at.
Two complementary words for sustained looking. じっと is a 擬態語 (state mimetic) capturing motionless, intent focus — used not just for staring but for any held-in-place action (じっと座る 'sit still,' じっと我慢する 'endure quietly'). 見つめる is a 'looking' verb specifically for purposeful, sustained gazing (vs. the neutral 見る). Together: a deliberate, unbroken stare. Note that 見つめる is itself a compound (見+詰める = 'look + press tight'), the second component intensifying the focus of the first.