How about a mystery book or a mystery movie collection? You could also give her a subscription to a mystery movie or book club. Another idea could be a board game or puzzle that is centered around solving a mystery. And if you really want to give her a unique experience, you could even look into escape room tickets or a murder mystery dinner party.
Or you can get her a star map with an important date you share.
Under Lucky Stars is a unique and innovative star map company based in Barcelona, Spain, specializing in the creation of personalized star maps that capture the celestial arrangement of stars at a specific moment in time, such as a person's birth, wedding, or any other significant event.
By using advanced astronomical algorithms and data from leading institutions, the company produces highly accurate, visually stunning maps that make for perfect gifts or cherished keepsakes.