。
She received a dismissal notice at work.
Literal
She [topic-は] company [at-で] dismissal-notice [object-を] received.
解雇 is the formal-register word for 'dismissal, firing,' and 解雇通知 is the notice that delivers the news (whether on paper or, increasingly, by email). The で marks 会社 ('the company') as the location where the event happened — 'at the office, at work' — rather than the agent (which would take から or に if expressed at all). The ~ました ending keeps the report neutral-polite. In casual speech a Japanese speaker might say 首になった ('got the axe'), but the formal register here keeps things matter-of-fact.