The 23-year-old model took to her Instagram account to hail the iconic star, who was born on September 10, 1933.
Alongside a series of images of herself and Lagerfeld, she wrote: ''Happy Birthday Karlito. We miss you and we love you forever.... [love heart emoji] (sic)''
The legendary designer passed away at the age of 85 in January last year from complications of pancreatic cancer.
During his career, Lagerfeld served as the creative director of the French fashion house Chanel from 1983 until his death, while he was also the creative director of Fendi.
Bella's Instagram tribute was posted shortly after it was announced that Kim Jones is set to replace Lagerfeld at Fendi.
The 47-year-old designer will be responsible for the brand's haute couture, ready-to-wear and fur collections for women.
Jones will also retain his position at Dior Men's, having taken on that role in June 2018.
Fendi's chief executive, Serge Brunschwig, hailed the appointment, describing Jones as ''one of the most talented and relevant designers of today''.
The London-born fashion designer is also looking forward to the challenge of his new role.
He recently said: ''Working across two such prestigious houses is a true honour as a designer and to be able to join the house of Fendi as well as continuing my work at Dior Men's is a huge privilege.''
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