。
She seems to be involved in the murder case.
Literal
She [topic-は] that murder-case [target-に] involved is seems.
関与する ('be involved in, take part in') takes に for the matter of involvement — に関与する is the standard collocation. Heavier and more formal than 関係する ('relate to'); 関与 implies active participation rather than mere connection. ~ようだ adds inferential softening: based on observable evidence, this is the speaker's tentative conclusion. The combination is the kind of careful phrasing one finds in journalism or detective fiction — pointing strongly without making an outright accusation.