I adopted a mix breed from a shelter over a year she is believed to be about 1.5 now. Why can't I break this dog out of her shyness. She is afraid of everyone and hides in corners. I am the only one she follows, we are always praising her and rewarding her but she still shows signs of being afraid. Help..

It's possible that the rewards and praise are actually reinforcing the shy behavior, depending on when you do them. You might want to talk to a behaviorist about the situation and see if he can give you some guidance on how to handle it. Or look for a trainer with a "shy dogs" class.

Thanks for the suggestion on Oreo. I will look into getting some therapy for me and my dog!!

My advice is to pick up a book and learn about being the pack leader. The dog shouldn't rely on you for security but shouldn't be dominant either so you have to find the middle ground. This is also important because the dog needs to understand you are in charge and can keep her safe (same psychology of an aggressive dogs, they turn to aggression because they feel the need to protect themselves because they don't have a leader to protect them)The most important thing you can do is ignore her shy behavior, avoid eye contact when she is unsure of herself, never ever shield her from anything or force her to inspect it. A dog trainer may tell you to use positive training methods so ignore the bad, praise the good (very very good confidence builder) Here are some exercises I use with my mutt, I build my dogs confidence by making him sit and stay on the deck and I hide his stuffed duck around the house, when I give him the OK, he searches for it and when he finds it I say 'There it is!! Wwwoooww!! ' Also any basic dog commands can build confidence...
Be patient she may need a few months of therapy.

Thanks for the feed back on Oreo. I will work on getting assistance on her behavior, I will be leaving for college soon and it's imperative that she gets out of this stage before I leave for school and then my mom is left with the situation,, Thanks again... Where is Cesear when you really need him!!

There is a book about shy dogs written by Patricia McConnell. Can't remember the exact title, something like "Your Shy Dog". Check on Amazon.com--its a pretty short book, but has a very common-sense approach.