。
She works in social welfare.
Literal
She [topic-は] social welfare [to-に] is-engaged-in.
携わる ('to be engaged in, take part in') is a slightly elevated verb favored when describing someone's professional involvement in a field — 'to work in,' 'to be involved with.' It pairs naturally with abstract domain nouns like 社会福祉 (social welfare), 教育 (education), 研究 (research), and gives a sense of meaningful, sustained participation rather than just doing a job. The ~ている is the resulting/ongoing state — she has been and is currently in this line of work. The whole formulation lands somewhere between everyday and CV-prose register.