。
She's just as pretty as her older sister.
Literal
She [topic-は] older-sister same-as pretty.
同様 ('the same, alike, identical in manner') functions as a noun-modifying suffix here: 姉同様 ('same as the older sister'). Slightly more compact and writing-flavored than the fuller ~と同様 ('same as'). きれい is a na-adjective covering 'pretty, beautiful, clean, neat' — its sense settles based on context, with people generally pulling the 'pretty/beautiful' reading. The adjective stands as the predicate without an explicit copula, conversational style.