。
Her work got easier.
Literal
She [topic-は] work [subject-が] easy became.
楽になる ('become easy, become comfortable, get easier') uses the standard Japanese pattern for changes of state: na-adjective + に + なる. 楽 ('easy, comfortable, relaxed') is a versatile na-adjective covering both 'physically comfortable' and 'easy/effortless.' The same construction works with i-adjectives by changing the い to く: 暑くなる ('become hot'), 高くなる ('become expensive'). A double-subject reading — '*as for her*, the work became easier' — gives a frame where the speaker isn't necessarily talking about the work itself becoming objectively easier, but about her experience of it.