2 aussie shepards and now a border collie

Question
my husband and i adopted a female (roughly 1 year old) border collie from the shelter that i work at about 2 wks ago. (her name is rose) we already had 2 aussie shepards-1 is a red double merle male named bandit who is 2 and the other is mystic who is a female blue merle that will be 4 in july. we also have a 3 yr old son. the first couple of days went rather well concidering she came into the shelter as a stray ( was only there a couple of weeks) and all we knew is that she could be defensive at times with other female dogs. she was also depressed the majority of the time b/c her buddy that she came in w/got adopted w/out her. we introduced everyone slowly with rose on a leash and when it was time to come in after hours of all of us being outside, i put rose in our large crate to get accustomed to the sights and sounds and smells of our house. we left her in there for about an hour to hour and a half and then allowed her to come out and explore a bit. she eats well with my husband and i around at the same time as our aussies and there isnt ANY kind of agression towards us humans at all. rose and our male get along very well which we did expect-she also loves our son and gets along well with our female the majority of the time. my concern is when all 3 dogs play. our 2 aussies are used to playing a bit loud and to someone who doesnt know there growls or barks it may sound like they are getting mean-but they arent. we have had them since puppies and know them very well. they play rough only with eachother and gentle with our son. while they are playing (the 2 aussies) rose watches w/her ears perked and tail wagging and eventually tries to get involved. my husband and i are still obviously learning her sounds and cues but watch and playfully encourage "play nice" tactics. rose seems to take things a bit personal after a few minutes. she starts to show her teeth and get stiff so we stop everything and tell her specificlly "no-play nice". she stops and they continue but then a few minutes later it happens again. now our 2 aussies are pretty laid back unless they are pushed. all 3 are fixed and work for a living-treats, food, up on furniture and stuff lke that. we also have always gone in 'pecking order' as well-mysic was first, bandit 2nd and now rose so that is how they get fed and treated, even brushed daily and for bath time every couple of weeks. we do not at all encourage 'let them fight it out so they can figure who is more dominant'-reason being we know that in the wild, whomever loses the fight-leaves the pack to find another. our house is not the wild and these are domesticated animals. i too have worked as a vet assistant and now work full time in a shelter/rescue center for animals-so im familure with some training tips and such but this is kinda worrying me b/c i would like to nip this in the bud (if there is anything we can do) rather than wait it out and let time tell. my husband feels that it will take time for rose and the other to adjust completely-which im ok with. but i also dont want to let it ride out if this wont resolve itself. mystic is 61 pounds and bandit is 58. rose is only 28 pounds and the smallest (not by much by height). they eat 2 meals a day as wellas treats thru out when they are good or do special things. mystic loves frisbee-bandit loves football and rose so far loves fetch in general. so we always have 3 toys going either outside or in.  all 3 have very good herding traits for not working on a farm and love to play. rose also stays in the crate w/ a water bottle attatchment and chew toys w/ a blanket when we are at work. she is house broken-and very rarely even wants up on the furniture and thats only when my husband or i are there to begin with. we relize they arent called bithes for nothing-and we really want to keep her so sending her back to the shelter isnt an option-unless she attacks but even then im sure (i would hope) training would help. we both have grown up with animals all our lives, particularly dogs. but neither one of us honestly ever had 2 females at once so we did do some research about how to introduce and things in general have gone quite well. like i said-im just asking for some advice to help speed things along (rather than just time) to help all 3 play together without rose taking things so persoanl.
i aplogize for such a long entry but i wanted to give you as much info about the situation as possible so you could have a better understanding of my concern. any advice would be greatly appreciated! thank you in advance.

Answer
Bobbi, I appreciate you giving me so much info! I do want to say, though, that you may never really be able to allow all three dogs to be loose together. I have basically the same situation as you; I had my pet dog, Gypsy (spayed female), then got Jak (intact male German shepherd) a year and a half ago to train for Schutzhund. They have always been great with each other, from day one. This past November, I brought Jessie (intact female German shepherd) into the home, and while she plays wonderfully with Gypsy and Jak if it's just the two of them, the minute I introduce dog #3 (no matter what order), things get tense. Jak believes it's his duty to 'protect' Gypsy from Jessie, and he 'corrects' her every time she tries to play with Gypsy. As a result, this gets Gypsy in a more dominant state of mind, and *she* starts being a little witch towards Jessie, even though they may have been playing just fine 2 minutes ago. It's all about pack dynamics. Three dogs is a pack. I've pretty much just given up on the idea of letting them all three play together at the same time, and only allow 2 of them out together at a time. It keeps the peace and keeps everyone's stress levels down.


On the other hand, it could just be that Rose still needs some time to adjust, and feel like she is part of her new pack. I believe you are doing everything right, and if you keep it up, they may be able to coexist happily with one another, even when unsupervised.


"we do not at all encourage 'let them fight it out so they can figure who is more dominant'-reason being we know that in the wild, whomever loses the fight-leaves the pack to find another."

This is not always true. Dominance scuffles occur quite a bit in wild canine packs without the 'loser' leaving. Usually, it's only when the alpha is defeated that he is 'kicked out' of his old pack, but, on the same token, I do not believe you necessarily NEED to let your dogs fight it out to determine who is more dominant. You, as the alpha, can step in and end it, but you need to be sure you can tell who the more dominant one IS, because if you choose the wrong dog, the fights could just get worse and worse. As I said, I think you're doing everything right, and just need to give it a little more time. Remember, it's only been 2 weeks.