The pronoun in the sentence is her, a possessive adjective describing the book as 'belonging to her'.
Because you don't know whether it is Lucy's day off or Linda's day off. Or to use your more proper lingo, it is because the antecedent of the pronoun is unclear. If the sentence is grammatically correct, it means Linda's day off. This question is confusing because the reader can not be sure whose day off it is. Lucy (on her day off) called Linda; Lucy called Linda (on Linda's day off answer;the antecedent of the pronoun is unclear
Lucille "Lucy" Esmeralda McGillicuddy Ricardo's birthday is August 6 , 1921 .
Here's Lucy - 1968 Lucy's Birthday 1-8 is rated/received certificates of: Australia:G
John Lucy was born in 1859.
Lucy Benjamin was born on June 25, 1970.
Lucy Davis was born on January 2, 1973.
Lucy Pinder was born on December 20, 1983.
Lucy Gordon was born on May 22, 1980.
Lucy Hale was born on June 14, 1989.
Lucy Benjamin was born on June 25, 1970.
Lucy Durack was born on November 17, 1982.
Gary Lucy was born on November 27, 1981.