Hello. Thanks for writing in. This can definitely become a serious problem if this continues as she grows older. It sounds like she has a very dominant personality. She needs to understand that you are the alpha of the pack, not her. It starts by making her understand that nothing in life comes for free. She has to work for everything you give her, including attention. This is where getting her to learn the basic commands of sit and stay is essential. She must follow these commands for any attention, treat, food, etc. At the same time, I would correct her with any type of physical punishment, no matter how mild. This may only challenge her more and make issues worse. Lack of attention and "time out" when she behaves like this will make her learn faster. I highly suggest that you get her into some puppy training classes immediately. You are going to need the help of a certified dog trainer to help you through this and work one on one with you to teach her discipline. You may even want to get the help of a veterinary behaviorist. The longer the behavior continues, the harder it will be to break her of this habit. If the training and time commitment seem like too much; it may be a better idea to return her. It will cost you a lot less heartache in the end. I have included a website that goes over this problem in more detail. Please let me know if you have any other questions. Hope this helps

http://www.peteducation.com/article.cfm?c=2+2085&aid=2415

http://www.petplace.com/dogs/dominance-aggression-assessment/page1.aspx