This shouldn't be happening to little kids, no matter what. Sounds like she has some serious issues.
I guess I could share a semi-related story, it's somewhat similar but without the fighting part...
When I was about 6-7 years old, my parents split up. They didn't divorce at the time, they just legally separated and my mom moved out of the house. I stayed at home with my dad (GVod bless him, may he R.I.P.

).
That decision was made because he and my mom got together and decided that I was closer to my dad at the time, therefore it would cause less problems if I stayed with my dad instead of moving in with my mom.
The same thing happened when they officially divorced in 1996. I stayed with my dad because they saw that I was closer to him and they wanted to cause as little distress to me as possible.
Which, TBH; I was frankly quite thankful for as at the time our move to Florida (which already had me upset enough) was being discussed.
