Mum and Ben lose Grandma's dog, and find a similar one at the shelter for her. Grandma has already found Pippa though, and so ends up with 2 dogs - Pippa and Poppa.
Found this while weeding our easy readers and read through it because I love dogs named Leo. A child and his mom are watching his grandma's dog, Cleo. When Cleo runs away, the boy and his mom search everywhere, with the local animal shelter being their last stop. There they find Leo, a male version of Cleo. They decide to give Leo to grandma instead of Cleo, though it's not explicitly stated whether they are trying to pass Leo off as Cleo or just offering a replacement dog. Anyway, Cleo ran back to the grandma's house, so she already has her dog back. In the end, she decides to adopt Leo anyway and have two dogs. Dumb.