。
She seemed disappointed with the result.
Literal
She [topic-は] that result [at-に] was-disappointed appearance-was.
がっかり is a 擬態語 (state mimetic) — the soft, deflated 'sigh of crushed hope' that you can almost hear in the word itself. Pair it with する for the verb. The closing ~様子だった ('had the appearance of...') is one of several Japanese strategies for describing someone else's apparent inner state without claiming to know it directly: 'she had the appearance of being disappointed' rather than the bald assertion 'she was disappointed'. Together with the third-person inner-state convention, this kind of evidential hedging is everywhere in third-person narration — Japanese is meticulous about marking the difference between what you see and what you infer.