。
She has tremendous respect for her homeroom teacher.
Literal
She [topic-は] homeroom [genitive-の] teacher [object-を] extremely is-respecting.
担任の先生 is the standard phrase for 'homeroom teacher.' Japanese schools assign each class a 担任 ('person in charge') — a single teacher who handles roll call, school-life guidance, parent communication, and (in lower grades) most subjects. The relationship is closer and more responsibility-laden than an English-speaking equivalent. 尊敬する takes its object with を, not に — different from 憧れる ('admire / look up to'), which takes に. The polite ~しています frames this as her ongoing state of respect.