。
It seems she really did witness that accident.
Literal
She [topic-は] surely that accident [object-を] witnessed [apparently-らしい].
There's a subtle semantic dance here: まさしく asserts certainty ('without a doubt') while らしい hedges it ('apparently, it seems'). The mixture isn't contradictory — it reads as 'apparently, and quite definitively at that, she witnessed it.' らしい marks the claim as inferred from indirect evidence (a report, observation, reasoning), so the speaker is saying 'from what I gather, she really did see it.' 目撃する is a Sino-Japanese compound — 目 ('eye') + 撃 ('strike') — meaning 'witness firsthand.'