First - thank you all for your in-put! It was very helpful.

My first dog died at 17 yo and I believe she had Alzheimer's. Her behavior changed drastically and she got quite unpredictable. I really don't think Bossy has that problem - she has always been bossy! She's just pushing Timid more and more. I watched The Dog Whisperer dealing with a similar problem and he said, that this is the way they treat omegas, and that it is this way, because dogs understand that. According to him, treating insecure dogs like insecure children is a big mistake. I will keep an eye on her and will take her to the dr. if things get weirder.