I believe it takes a few days to buy a gun, you can't just get one. Unless it's one of the states where you can.
But yeah, 100% guaranteed way to prevent it is to kill him first. Any other solution has a failure condition.
Cause if she tries to get him arrested and there's "not enough evidence" and he kills her for trying, you'd probably just shrug and go "Why didn't she move out?".
That's why she should be bumped up on the processing priority list should she show evidence of Domestic Abuse and have a Police Report.
The Police themselves or certified local instructors should be put on priority training her and arming herself effective immediately of Documented Proof of abuse from their Spouse / Significant Other.
Also putting them into a semi-Witness Protection service where she modifies all of her Official Documents, change her Accounts, close old accounts and move the funds to new ones.
All that should get special priority so she can become a new person in the eyes of the government while moving up her Divorce Proceedings in the Docket along with a restraining order.
They should also have a tracking ankle bracelet on the Abuser and Abusee with a simple app to warn the Abusee approximately how close the person is on a GPS level. A simple (Distance Away in Km/Mi) would be sufficient without exposing exact details to the Abusee should she want to go "Kill them first" mentality.
lmao Dude just pulled this out of his ass, and thought it was genius. ---
