。
She angrily left the room.
Literal
She [topic-は] got-angry [and-て] room [object-を] exited-and-went.
出て行った is a compound directional verb: 出る (exit) + 行く (go), expressing movement away from the speaker's location. The て-form of 怒る sets up the emotional backdrop for the action. を marks 部屋 as the space being departed — this is the 'departure を' used with movement verbs, distinct from the standard object-marking を.