I do not think this is a pack heirarchy issue. I think dominance and heirarchy are used way too much to over explain what are just behaviour issues.
Tessie has been there for 2 years and suddenly you added not one, but two other adult dogs. This was going to be very unsettling for her and it sounds like she has coped wonderfully well. A bit of snarling is a minor issue. All that's happening is she is saying - 'bugger off this is my spot' and it sounds like the other dogs are accepting of that. If you want the other dogs on the bed as well then there are approaches for helping Tessie feel more secure in letting them on the bed or near anything she is guarding.
Sorry I do not agree with the others. I think this is best dealt with using a positive, reward based approach so she feels its a good thing the other dogs are there. Punishing her will just add to her insecurity and could make matters worse.
I wouldnt worry that she is doing anything to undermine you as a leader.
Agree with this. The whole "dominance" thing is outmoded and desperately simplistic, propagated mainly these days by the likes of Cesar Milan and not by qualified dog behaviourists.



I admit my first post might have seemed...curt. I probably didn't put the effort into it I could have.