。
She looks up to her older brother.
Literal
She [topic-は] older-brother [toward-に] admiration [object-を] is-holding.
抱く ('to hold, to embrace, to harbor') is the standard verb for 'holding' an emotion or thought as if it were an object — 希望を抱く ('hold hope'), 疑問を抱く ('harbor doubts'), 不安を抱く ('hold anxiety'). The に here marks the target of the feeling — 'admiration toward her brother.' あこがれ ('admiration, longing') has a romantic, aspirational tinge: it's the feeling of looking up to someone you'd like to become like, not just a neutral respect. 兄 specifically means older brother; younger brother is 弟. The hierarchical sibling distinction is built into the language.