。
She's honest in everything.
Literal
She [topic-は] anything [in-にも] honest is.
何事にも is the にも variant of the universal-quantifier pattern: 'in every matter, in all things.' The に attaches the universal frame to the predicate (here, 正直 'honest'). Compare 何事も (with も alone) which often pairs with verbal predicates, while 何事にも is preferred when the universal scope modifies a state predicate. 正直 ('honest, frank, truthful') is a na-adjective often used in praise of straightforward character.