Alcohol use/abuse in and of itself is insufficient reason for psychevaluation in most states and throughout most of the world and this is probably for the better, as most people would have to be incarcerated in psych. wards at some time. However, if there is a direct threat to themselves or to others, as in the instance of an attempt at self harm, then there are several options open to the discretion of the courts.
As most evaluation and asessment centers are chronically over utilised and underfunded the courts have only a limited recourse to the services. Therein there is therefore a considerable paradox. In the case you mention where dual diagnostic disfunction seems to be at the forefront, the issues become more problematic.
Unless there is probable cause to reasonably suppose that a person is so mentally unbalanced as to pose a direct threat to themselves or to others there is very little that can be done either within the justice system or within the constructs of an ex-relationship situation. The police are certainly not experts at what constituates a psychotic disability, nor for that matter are the courts.
Even in an involuntary commitment to an A and E Facility a person so committed may discharge themselves after 48 hours or earlier, depending on the need for triage assessment, from any facility.
You are truely at a disadvantage. Only a Psychiatric Evaluation whereby an offence against the precepts of law is evident, may a court order a committal order for assessment and evaluation. This is an ambiguity and the main reason for for so many folks having to take to the streets and living a substandard life.
Be strong and surround yourself with support of your own to help yourself through a very trying situation.

I wish you well and I hope you find some peace for yourself. There is nothing you can do for an addict who will not admit they have a problem. There's a saying in AA, Let Go and Let God. That goes equally well for the families/friends of alcoholics, you have no control.

As for the mental illness, until there is a diagnosis, again, there's nothing you can do. But, in your community, there should be an agency dealing with mental illness. Contact them, explain the situation and see if they can help. Usually, though, there needs to be an immediate family member who institutes involuntary proceedings. You are not, again, this is not something within your control. All you can do is learn to accept that, learn to accept you've done what you can, the rest are the choices of the person.

Catsloveme, You said that she apparently is the luckiest DUI driver in the world. The people on the road are the luckiest people for not having been killed by this woman. Next time you see her get into a vehicle you need to call the police. You might add that you THINK she has a gun. That will get her some extra attention immediately.

I agree with that, most addicts have to reach such a low point in their lives before they'll admit they have a problem. For many, jail and the expense etc of a dui works.