。
She came to France to spend her vacation.
Literal
She [topic-は] vacation-spending [for-に] France [to-に] came-along.
休暇過ごし is a noun coined from the verb stem 過ごし ('spending, passing [time]') prefixed by 休暇 ('vacation'). Japanese forms many such 'X-doing' nouns by attaching a noun to the masu-stem of a verb — 時間つぶし ('time-killing'), 山登り ('mountain climbing'), 一人暮らし ('living alone'). The に after this noun is the 'purpose に' — verb-stem (or activity noun) + に + a motion verb to express going for the purpose of doing X, as in 買い物に行く ('go shopping') or 散歩に行く ('go for a walk'). やって来る reappears here in its arrival sense: she came (all the way) to France for the vacation.