。
She should eat breakfast.
Literal
She [topic-は] breakfast [object-を] ate [better-方がいい].
~た方がいい gives advice or a recommendation: 'it would be better if (she) did X.' The past tense 食べた (not 食べる) before 方がいい is standard — despite recommending a future action, the pattern uses た-form. The nuance is milder than a command but more pointed than a suggestion.