。
Unlike her mother, she is tall.
Literal
Mother [from-と] different, she [topic-は] height [subject-が] tall.
~と違って ('unlike X') is a fixed comparative, the te-form of 違う ('differ') — 'being different from X,' which reads as a circumstantial 'unlike.' 背が高い is the standard 'tall' construction for people: 背 ('back, stature') takes が as the subject of the い-adjective 高い, not を.