I read your request several times to be as sure as I could that I was reading it correctly. If I am reading it right, you do have a serious problem that will only become bigger as time passes.
I would suggest you read your own letter again as someone from the outside looking in. It appears you have placed your child and your dogs on equal ground. You refer to your child and the dogs as siblings. You then refer to all as critters. That is unhealthy for all in your house, human and dog.
You've had the dogs longer than the child and it is understandable that you love your dogs. You stated that Belle is "yours". It seems you have made the mistake of many dog owners of "humanizing" your dogs, especially Belle. In your daughter's eyes, you give much more attention(love) to the dogs than to her. You send your daughter to time out to teach her to respect the dogs. Are the dogs ever sent away to make space for just your daughter? Is there ever time she is with you without the dogs being present? If not, then what you are teaching your child is the dogs are more important.
You began teaching your child from an early age to respect the dogs, but did you teach the dogs to respect your child?
No matter what we think, or how much we love our dogs, or how much we confuse them by projecting human attributes on them, they are still dogs. Pack animals by nature. Whether you realize it or not, or accept it or not, you have a pack and pack order which includes the humans in the house. From your letter, it seems Belle is the pack leader, you follow behind her, then the other two dogs, then your daughter and husband.
When you tell your daughter that you love "all your girls", you basically equate her as a dog. When you tell her the dogs are as special as she is, you send the same message. Your daughter's actions toward the dogs are to be expected as she has to compete for your attention and does a human version of the pack behavior of moving up in the pack.
I see one of two things happening. Your daughter's attempts to place herself at the top of the pack will continue to escalate, she will become more aggressive toward the dogs, as that's the way dogs do it and your have taught her dog behavior is preferable to human. This will also be her behavior toward other children, as that will be the way she has learned to deal with issues.
Or, your daughter will give up on trying to move up in the pack and withdraw from you. She will give you all the space she thinks you want with the dogs. Your own words state that you "make space" for her, but the dog was there first.
Your daughter needs to know that she is your daughter and the dogs are the dogs. Your dogs need to know that this child is above them in the pack.
If you already refer to your daughter and the dogs as your girls in your home, as siblings, you will most likely do it with others outside the home. This will be most humiliating to your child and if other children hear this kind of statement, they will, as children do, repeat and expand those statements. This could cause great emotional damage to your child.
There is no reason that all critters in your house cannot cohabit happily. It is a matter of changing perceptions and perspective. Ask yourself the basic question. Why do you have the dogs? Companionship, affection, come when they are called(on demand), entertainment? They are, basically, your toys. Why do have a child?
We can love our dogs as much as we love any human, however, we must show that affection to each in it's proper manner. It's very confusing to dogs to be treated as human and vice-versa. Perhaps you really do love your dogs more than the humans in your house. It's not all that uncommon. If that's the case, you simply need to acknowledge the fact to yourself and deal with it.
I read another post that suggested you don't have to prove you love you daughter more than the dogs. I disagree with that. By "making space" for your daughter among the dogs, by punishing her for competing for your affection, you are proving to her you do love the dogs more. Kids are so often on target with their summation of a situation and honest about it and their feelings on the subject.
I highly recommend you watch the Cesar Milan Dogwhisperer program on NATG channel. You might also check his website for books and DVDs. This man has great insight and advice for dog owners who have, without realizing, let the dogs become the pack leaders of the house. It happens even with the seemingly most docile and lovable dogs.
It really is up to you. You are training the entire household. You love your husband and child, you love your dogs, but truthfully, one or the other has to come first. Whether or not you say it, put it verbally, your actions will tell both who really is first.