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She wears the same kind of clothes as her older sister.
Literal
She [topic-は] older-sister [subject-が] wear [nominalizer-の] [comparison-と] same kind [genitive-の] clothes [object-を] is-wearing.
Two small choices set the rhythm. 姉 (without さん) is slightly more direct and less familiar; 着ている (rather than 着る) shifts to the resulting-state ~ている: with clothing verbs, ~ている often expresses 'is wearing' as a state — '[she] is in the state of having put on (clothes).' This 'state-result ~ている' pattern is one of the more confusing aspects of the auxiliary for English speakers, who expect progressive 'wearing' to track the act of putting on rather than the resulting state. The embedded comparison uses の to nominalize 姉が着る ('what her sister wears'), then と同じ for the standard of comparison.