She claims to have used such items for: planned events and surprises.
Explanation:
The easiest way to check to see if a colon is used correctly is to read the entire sentence BEFORE the colon. If it's a complete, independent idea, then the colon is correct; if not, the colon is incorrectly used. In the correct answer to the colon being used incorrectly, the sentence before the colon is "She claims to have used such items for". This is not a complete, independent idea. The preposition for needs an object. The guidelines also tell us that colons do not come after prepositions.
