[observer]

Yes, it is terribly painful. But, as you already know, your first responsibility is to your children. You have to keep them safe. If she is, in fact, just not wired correctly, (and a dog that truly does what she does without warning is not, but sometimes there are warning signals that the owner doesn't pick up) that is not a happy way for a dog to live. Those demons will not get better. The liability you would face, should she hurt someone, can be huge. As she gets older and larger, she will be even more dangerous. It is certainly not "immoral" to put such a dog to sleep.

EDIT: If a knowledgeable trainer/behaviorist is able to fully evaluate her in person, I agree that you should do that first. If the conclusion is the same, at least you can have the peace of mind that someone who is an expert actually evaluated her in person first.

There have been others here who have had to make the same decision you may be facing. A search on "demons" should lead you to some of those.