Separation Anxiety

So i have been looking around on the internet and did a prelim search on this site, still have my lingering question: Does my dog have separation anxiety? She is a four year old dachshund that we rescued through the DRNA. It is only her third week with us, and previously one week with the foster parents - meaning she is less than a month from being in the abusive home that gave her up. She doesnt know many commands and had never been walked on a leash or worn a collar. She has been so fantastic about learning new things and going potty outside. Now here comes the issue. When we leave the house, she flips! Not in a destructive way, but whines and howls ALL day and recently (last two days) relieved herself on the kitchen floor. We do have her crate trained, but she is puppy gated in the kitchen with her bed, her crate, some toys, some water and the radio during the day. When we are at home, she sits quietly or naps on her bed when we put her in the kitchen. We are pretty sure that she is grasping that we are the alphas - she follows behind on the leash, lets us enter rooms first and we eat before she does (all lovely tips culled from our DRNA rep, Cesar Millan and some books). So my long-windedness reaches this: what can we do for our lovely girl? Affordable behavioral training that addresses this issue in the nabes? Helpful hints or tricks anyone out there may have had success with in a personal or third-party way? What about a D.A.P diffusers (do they work?)? Any assistance would be GREATLY appreciated!