Major dog problems!?

My female dog Athena trys to run away all the time so I got her deed thinking this would slow her down (& so other dogs can't mate with her) But she still keeps getting out. We have 6 foot fences so she's not jumping. We take her for walks regularly and she's allow inside whenever were home and have another dog to play with. I just don't understand why she wants to run away and how I can stop her! (We can't afford to keep getting her out of the pound)