。
She found me a good seat.
Literal
She [topic-は] me [to-に] good seat [object-を] found [for me-てくれた].
見つけてくれる ('find for me') is the productive ~てくれる auxiliary attached to 見つける ('find, discover'). よい is the somewhat formal/written equivalent of いい ('good'); both are correct, with よい slightly more careful. Note that よい is the dictionary form, while いい has displaced it in everyday spoken use except in fixed phrases (よろしい, よかった) and certain inflected forms.