Her unexpected visit was ________ to everyone at the

Solution

The word "delightful" best fits the context as it suggests that the unexpected visit was pleasant and enjoyable for everyone at the party. Irrelevant means not related or pertinent, which does not fit the positive impact implied. Routine implies something ordinary or expected, which contradicts the idea of an unexpected visit. Unremarkable means not noteworthy or significant, which does not convey a positive impact. Delightful is the most suitable option to fill in the blank.