。
She's much taller than I am.
Literal
She [topic-は] me [than-より] much stature [subject-が] is-high.
Two notable points. First, the comparative より paired with the intensifier ずっと ('much, by far') yields 'much more than,' the standard way to mark a large gap in degree. Second, 背が高い is the conventional Japanese way of saying 'tall' — literally 'the stature is high.' 背 ('stature, back') takes が as the subject of the i-adjective 高い, even though English would treat the person as the subject. This 'X is large/small in respect to Y' frame, with Y as a body-part subject, is widespread (頭がいい 'smart' = 'head is good,' 鼻が高い 'proud' = 'nose is high').