My Address has been changed 3 times by a spiteful ex, how do i correct it and prevent it?

Hi, My father is trying to divorce a bipolar psycho lady who is now trying to ruin our lives. She has changed our mail address 3 times which has made our bills late, ruining our credit, and is screwing up our credit cards and bank accounts. We also know that she has been taking mail from our mailbox. We've both contact USPS about her changing our mail address and mail tampering but they just said " They'd look into it" That was about 2 months ago and she just did it again! What do I do to make her stop!? Are there any legal actions I can take against her? Any advice would be appreciated.