。
She's bound to win the tournament.
Literal
She [topic-は] surely tournament [in-で] will-win-championship [probably-だろう].
優勝する ('win the championship, take first place') is a sports-and-competition-specific verb — distinct from 勝つ ('win [a single match]') in that 優勝 implies overall victory in a tournament or league. The で here marks the scope of the win — 'in the tournament.' トーナメント (loanword from English) refers specifically to elimination-style tournament structures; round-robin formats are usually リーグ戦. The whole structure projects confidence in a competitive outcome.