。
She's just as pretty as her older sister.
Literal
She [topic-は] older-sister [comparison-と] same-way [as-に] pretty is.
~と同様に keeps the equal-comparison frame straightforward: と marks the standard, 同様 ('same manner') links them, に turns it adverbial. きれい is one of the most flexible Japanese adjectives — covering 'pretty, beautiful, clean, neat, tidy' — with context picking the dominant sense. Slightly more compact and conversational than the more polished 魅力的 (an alternative that uses the productive ~的 suffix).