I hope this puts some light into your situation. I have been an obedience instructor for years .... It could be a number of things as to why your new dog is reacting in such a way. Do you know where she came from prior to your home (living situation and treatment)??

First of all, I agree with the others - she is adjusting to an environment and needs time. Secondly, obedience is an excellent idea BUT I always recommend you wait several weeks after she has been with you. The reason for this is...if you have a dog that is fairly shy and timid, throwing her in more of a hectic situation may have a reverse effect. Then, enroll her in some basic obedience and this will definitely help her. You may want to seek a class with a limited number of dogs or with more than one instructor.

If you have any other questions or concerns, I would be happy to help. Good luck.