How about getting her a Coldplay concert DVD set, such as "Live 2012" or "A Head Full of Dreams Tour"? You could also consider getting her any Coldplay merchandise, such as a t-shirt or poster, or a Coldplay vinyl record. Another option is to create a Coldplay themed gift basket which includes items such as CDs, song lyrics, concert tickets (if possible), and themed treats such as popcorn decorated in the Coldplay logo.
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.