take matters into one's own hands

これもReader's Digest 9月号の8th Annual Humour Issueにあった表現です。
As a burglar tried to enter the home of a woman, she took matters into her own hands. Getting on all fours, she barked and scratched ferverishly at the door. The thief was last seen running from the porch.
"took matters into her own hands" の個所は慣用句の様です。　辞書を見ます。
・Cambridge Idioms Dictionariy: to deal with a problem yourself because the people who should have dealt with it have failed to do so: The police haven't done anything about the vandalism, so local residents have taken matters into their own hands.: When the police failed to catch her son's murderer, she decided to take matters into her own hands.
他の辞書ではこの慣用句の説明は見あたりませんでしたが、これでRDの記事の意味は分かりました。もっとも、辞書の説明によると、泥棒に入られた女性は犬を飼っていたが、番犬の役目を果たさなかったので、彼女がその代わりをした様に思えますが、実際に犬を飼っていたのかどうか気になります。もっとも最近東京で見掛ける犬は猫と同じ位の大きさなので番犬の役に立たないのも不思議ではありません。