Now lemme break the structure down for you. 저: Demonstrative Adjective, 여자: Woman 는: Subject Marker. 키가: height, 이만큼: This much (demonstrative adjective, again) 큽니다: is big.
Adj. Subject. Adj. (Formed with a noun and a dem. Adj) Verb (that functions as an adjective). Since it's possible for a sentence to have no direct object, and korean's word order is SOV, this order is plausible, and it is common.
Big isn't accepted for me though, though I guess Duolingo prefers to use specific English words since big can pertain to other things while "tall" is the closest to mentioning 키.