New puppy.

Question
Hi! :] and thanks for helping.
Okay I have a chihuahua/maltese mix puppy, that ive had since February. Shes about 6 months now.  She gets along with other dogs well, she barks. But smells them and wants to play. But 2 days ago, my boyfriend bought a new 8 week old puppy, its smaller then her, we think its a chihuahua boston terrier mix?, so when he got her, we brought her to my house, and let my puppy smell her and stuff. My puppy seemed scared, but curious.  But then we left.   We came back that night, so that I could watch her while he went to work. And while she was here, my puppy started acting so diffrent. Like, she attacked the little puppy while eating a bone. (I have 2 other dogs, and she doesnt even do that to them)  and she gets like very defensive,, I think it has to do with the whole "whose the alfa dog" thing. But im just scared, cause shes never acted violently before, and I get mad at her, cause the other puppy is so small and  I dont want her to become violent.  I guess my question is,  Is this normal? And what can I do to stop it? And how long will it go on?

Answer
Hi, Tiffany,

Anytime a new dog comes into an already established pack (your 3 dogs), it alters the balance until they all work out the pack order.  A certain amount of squabbling can be normal, but if an all-out fight breaks out, you'll need to step in so that no one gets hurt.  

Allowing a situation where one dog has a bone and another does not is a good way to cause friction.  If one dog finishes their bone first, it's up to you be keep that dog away from the one who's not done yet.  The dogs may all have their position within the pack, but YOU have to be at the top of the entire household, and it's up to you, and your responsibility, to do what you can to prevent problems before they occur.

Here is some information on dealing with multiple-dog households:
http://www.ddfl.org/behavior/dominance.pdf
http://www.ddfl.org/behavior/dog-intros.pdf
http://www.ddfl.org/behavior/canine-rivalry.pdf
http://www.marinhumanesociety.com/Behavior/Handouts/MultipleDogs.pdf