Final answer:
Lucy described Isabella as her best friend, which indicates a deep and personal relationship, making her more than just a close friend.
Step-by-step explanation:
Lucy described Isabella as her best friend, indicating a deep and personal relationship. This goes beyond being just a close friend; a best friend implies the highest level of friendship and personal connection. Therefore, from the options provided, the most accurate description of Isabella to Lucy is as a close friend, but considering Lucy's own words, 'best friend' captures the essence of their relationship even more precisely.