Answer:
She is no longer beautiful because she has aged.
Step-by-step explanation:
The author literally asks that when she is old, wrinkled and gray, she takes the book, reads and remembers the belaza they had when she was young. The part of the text that makes this clear is:
"...take down this book, And slowly read, and dream of the soft look Your eyes had once, and of their shadows deep; How many loved your moments of glad grace, And loved your beauty with love false or true..."