。
She postponed her trip to Mexico.
Literal
[topic-は] Mexico-going [object-を] postponed.
メキシコ行き combines the place name with 行き ('going [to]') — a productive pattern: 東京行き ('Tokyo-bound'), アメリカ行き ('America-bound'). The reading is メキシコゆき or メキシコいき; on train signs and tickets, 行き is conventionally read ゆき. 延期する ('postpone, defer') is a Sino-Japanese formal-leaning verb — for casual contexts 後回し (lit. 'pushed to later') or simply ずらす ('shift') would feel more natural. The sentence has the matter-of-fact tone of news or travel diary entry.