。
She's involved in social welfare work.
Literal
She [topic-は] social-welfare-work [to-に] is-engaged-in.
社会福祉事業 is a three-part compound: 社会 (society) + 福祉 (welfare) + 事業 (enterprise/work). 従事する (じゅうじする) means to be engaged in or to work at — a formal verb for describing professional involvement. The ~ている marks this as her ongoing work. The vocabulary level is distinctly formal and written.