How can I get my dog to stop being so spiteful?

I have a 2 yr old dachsund who used to be the perfect dog. My old roommate and I both adopted these 2 puppies who were in a holding cage together. When they lived together they were both perfectly behaved, my dog especially perfectly potty trained, never chewed anything up, etc. Now I have moved back home to a different state and she is unfortunately all alone. SHe does nothing but misbehave, she pees wherever she wants (except outside where she is supposed to). She chews up everything and has no problem destroying anything in her sight. I am getting fed up and running out of ideas. Any suggestions?