new pet in the family

Question
I have a 8 year old Boxer and 2 year old Morkie both females with good dispositions.  We recently brought in a 6 year old ShihTzu female. The Boxer stays inside and outside the Morkie inside all the time and the ShihTzu has been staying inside too.  The Boxer had established herself as the leader with a pindown and hold kind of move towards the new ShihTzu.  The new dog was released after about 15 seconds umharmed.  So I thought they had settled any pecking order issues.  Lately however, the Shih Tzu will lurch out from under my chair towards either of the other dogs bark kind of crazily and then run back under my chair.  Any advice on how to help them all just get along.  Also the little Morkie tries to play with the ShihTzu by barking with her tail up and front paws down but the ShihTzu just does more of that lunging barking thing and hides.  :(

Answer
It sounds like the new Shit Tzu may be acting out towards both dogs after being pinned by the boxer. Do they ever go into the same area at the same time or is the shih tzu constantly avoiding both dogs, except for lunging from under the chair? It's hard knowing what kind of environment and how the it was handled/trained previously to know if there was any damaging effects we need to work through.

I always have good luck when food is a mediator. Try putting down some mouth-watering food, a dish for each, and see if they are willing to at least eat in the same room/area. We want the shih tzu to realize that the other dogs pose no threat. If they eat comfortably, great. Start moving the dishes closer together until they are side by side. If there is any growling/barking, use a spray bottle to show that that behavior is not tolerated. If the shih tzu runs and hides at some point, bring it back and start over.

If they already eat together, then when the morkie attempts to play, bring out the shih tzu and hold it and let them sniff each other. If the shih tzu resists, don't let go and reassure in a calm and gentle manner until it calms down. You can also use treats to reward when and only when she is providing the appropriate behavior.

Let me know if this helps and feel free to follow up if need be.