Wife and girlfriend (and tenant at the time) were arguing in our house. My wife got up from her chair and went up to her 'friend' and touched her on the shoulder where upon the 'friend' grabbed my wife by the throat threw her to the ground and dug her fingernails into her eye causing my wife's face to be bloody.

When I was called in, they were on the floor with this 'friend' on top of my wife.

Police said that because my wife touched her first, my wife would have to make a citizen's arrest and that they (police) would have to book both of them. She did not do this.

From what I can gather in CA touching someone on the shoulder (while arguing) could be considered battery however, is this gal within the law to mount that kind of self defense? Just wondering.