。
She doesn't look it, but she's a real go-getter.
Literal
She [topic-は] appearance [not-going-by-によらず] hard-worker is.
見かけによらず is a fixed phrase, literally 'not going by appearances,' used for surprising-someone-up assessments — 'you wouldn't think it from how she looks, but...' (the harsher cousin 見かけ倒し means the opposite, 'all looks and no substance'). The label 頑張りや (also written 頑張り屋) bolts the productive personality-type suffix ~屋/~や onto the masu-stem of 頑張る ('to persevere, give it your all') to mean 'a person who tries hard, an eager beaver.' The same suffix builds 寂しがり屋 ('lonely-prone person'), 怖がり屋 ('scaredy-cat'), 照れ屋 ('shy person'). 頑張る itself is one of those untranslatable Japanese verbs with strong cultural weight — it shows up everywhere from cheering on a friend to school slogans.