。
In her speech, she referred to World War II.
Literal
She [topic-は] speech [inside-の中で] Second-World-War [about-に] mentioned.
言及する is a Sino-Japanese compound verb ('reference + mention + do') belonging to the formal register — newspaper writing, academic discussion, and similar contexts. It always takes its target with に, never を. Spoken alternatives include 触れる ('to touch on') and 話す ('to talk about'). The phrase 演説の中で ('within [the course of] the speech') is a textbook use of の中で to localize an action inside a span of activity. The Japanese name 第二次世界大戦 ('Second World War') is a precise calque of the English; in Japan the war is more often referred to specifically as 太平洋戦争 ('Pacific War') for the Japanese theater, with 第二次世界大戦 reserved for the global framing.