( PEOPLE.com ) -- It 's been more than two months since their beloved 13-year-old dog Darla passed away from cancer , but Brooke Shields and her family are still reeling from the loss . `` It 's very sad , actually , '' she tells PEOPLE . `` We 're all in that sort of trauma where we have her ashes and the girls ( Rowan , 8 , and Grier , 5 ) carry these little footprints of hers around . She was the only dog we 've really ever had . '' The American bulldog was given to Shields as a puppy , and was a member of the family , taking a central role in many memories over the years . `` She knew I was pregnant before I even knew I was pregnant , '' Shields says . `` She would circle me and not let me walk anywhere , I was going , 'God , what are you doing , get out from under my feet ! ' And that afternoon I found out . '' The void that Darla has left is immense , and it wo n't be filled with a new pet anytime soon . `` We walk to school everyday and they see all these different dogs , we 're kind of [ thinking about ] what way do we want to go , '' she says . `` We 'll probably never get another bulldog . We would just constantly be going , 'That 's not Darla . ' '' For now , Shields and her family are content on seeing animals from afar -- like Mom 's new furry costar : a horse called Odd Job Bob who stars opposite Shields in the new tween flick The Greening of Whitney Brown . In the comedy , Shields plays the mother of a snooty private school teen ( played by Sammi Hanratty ) who is forced to move to the country where she reluctantly befriends the gypsy vanner horse . `` He 's smart and sweet , '' Shields says of the star stallion who performs all kinds of tricks for the film . `` He understands . There 's something about him that is human . '' A horse lover all of her life , Shields never got to ride Bob because trainers wanted Hanratty to bond completely with the animal , but she did slip him a treat or two on set . `` He was n't demanding at all , '' she jokes . `` He loved [ eating ] all the carrots and jam . '' Watching the sweet family movie with her daughters will definitely be a bright spot in what 's been a difficult few months . `` They 're going to love it , '' she says . `` Anything with horses and animals , they think it 's so funny . '' See the full article at PEOPLE.com . © 2011 People and Time Inc. All rights reserved .
Shields ' 13-year - old dog Darla passed away from cancer . The American Shepherd was given to Shields as a gift . The legacy that she has left is immense , Shields said .