Impulsive Bipolar Mother, Aggressive Dog, Injured Sister, Need Legal Options

My mom (F 37) drove all the way to Texas to get this 1 year old, male, still intact, rescue Great Dane. It ended up biting my sister (F 13) as soon as she pulled into the driveway. She has a huge hole in her arm and it's currently wrapped in gauze and needs to be cleaned multiple times a day so it doesn't get infected. Probably should've went to the hospital and gotten stitches. That was the night she brought the dog home. Instead of messaging the woman who sold her the Great Dane to see if she could get a refund, or posting the dog to rehome it, she KEPT the dog and put it in her backyard. She ignored all my advice on buying a muzzle IMMEDIATELY and putting it on him while he's home alone with my sister. She went to work and like clockwork, the dog broke down the back door and attacked my sister. She called the cops and animal control to come take and euthanize the dog. So the cops are there, animal control is there, 5 different members of our family are there because she's overdramatic and decided to "rally up the troops"... idfk.... and decides to keep the dog and just put him in "obedience school". All 5 of our family members are telling her to rehome the dog or euthanize him because he's dangerous and she's never home to train him or keep an eye on him. (She works night shift at a hospital) The only two people that side with her on keeping the dog and putting him through obedience school are the two cops (one police officer, one animal control officer) that don't even know her name. She gaslit the cops into thinking the dog just has "mood swings" and that he's actually a "good boy" and *potentially* just has trauma from *potentially* being abused. The dog bit the cop's hand after she said all of this. She's impulsive bipolar and just getting out of a divorce so she's spiraling. After the cop recommended a particular obedience school and gave the business card to my mother, everyone left, including the police. On the way home, I found out that my mother called my dad (they are separated) and asked for him to pay for the obedience school because she can't afford it.

What can I (F 21) legally do to get this dog out of her house so I'm not worried sick for my sister's safety 24/7?

TL;DR: My mother bought an aggressive dog that bit my sister and instead of rehoming the dog or euthanizing him, she decided to keep him and put him through "obedience school" which she can't afford and is having her ex-husband pay for.

Location: Mississippi

EDIT: Just got off the phone with CPS as I'm writing this, but I want more options