The link I found claims she is 12 years old..and as I suspected..she was told to do this by her parents, and had done it in the past.
TIPITV - UPDATE: Majka okrutne djevoj?ice podr?ava njen ?in: ?DA IMAM PU?KU POBILA BIH SVE PSE!''
A quick translation comes up with this....
This is the girl from the village of Bugojno in Bosnia, only 12 years old. Her mother, who sent a girl for the safety of relatives abroad, rules out talks with the child and pointed out that quite normal for them to kill the dogs because they bite and spread disease. In addition, he noted that it is terrible that the world pays more attention to animals than to man.