[yorkietalkjilly]

I imagine that little Chi walking about with her tail clamped down and living in fear is what the concern is by OP. It's bound to be a terrible way to live - awaiting attacks. As long as she is doing that - waiting for them in fear - they will likely keep happening. That dog's fear could be bringing on the attacks as some dog's want to attack what they perceive as instability or fear. Mostly I let dogs settle their own alpha type disputes but in this case, there is one dog living pretty miserable. Before the attacking becomes a longer ingrained problem and creates a fear-aggressive Chihuahua, I'd interfere and stop the attacker, working with her to make her understand she's gone past my - and that little Chihuahua's - comfort level and teach her who has the authority in our family and no more fighting. Once the aggressor is changed and under control, the OP can work to rehab the little Chi and her probable insecurities. I think the behaviorist is a great idea as that person can get to know what really is the problem as we all just have to give our best guesses with the limited information and not knowing the dogs involved. I'll bet the little Yorkie will be relieved eventually to have what she thinks of as her responsibility of correcting the little Chi removed from her shoulders.