。
She needs to help him out.
Literal
She [topic-は] him [object-を] help-do-for [need exists-必要がある].
~てやる is one of the giving auxiliaries: it marks the action as done as a favor for someone, with やる (vs. あげる) signalling that the recipient is socially equal-or-below the speaker, or close enough that humbling language isn't needed. Using やる toward another adult can sound a bit rough or even condescending — it's most natural between close friends, family, or toward animals/children. The construction adds 'doing this for his sake' beyond plain 助ける. ~必要がある is the standard 'need to / it is necessary that' pattern.