Aggressive Yorkie / Chihuahua Is A Jekyll & Hyde

by Dee
(Florida)

Hello,

We have had our Yorkie / Chihuahua mix since she was 6 weeks old. She bonded immediately with our 6 year old Chihuahua and -- for the last year and a half -- she would follow her about, sleep on her, and generally be happy just to be with her.
However, about 3 weeks ago, our little Yorkie / Chihuahua has started randomly attacking her "big sister" for seemingly no apparent reason. It has happened on five different dates, at different times of the day, and in different places. Each time, it is terrifying because it's like a switch was flipped and she instantly and viciously turns on the older dog. The older dog doesn't defend herself well and the Yorkie / Chihuahua literally won't let go until she is pulled away.

This is a 360 degree switch from her normally cuddly, loving, and non-stop kissing personality. In every other respect she is terrific -- comes on command, waits for treats until given the okay, stops barking at "no" and does not beg at all for food. She is one of the most affectionate dogs we have ever owned. However, I am too fearful this will happen when we are not present and I cannot fathom finding the older dog seriously injured. The last attack caused distress (and a couple of cuts) so I had to ask my son to take her to stay with him.

Is there a better solution?