After a DUI while on probation in college I had mandatory addiction counseling for two years. Woke me up, got me sober. If she is willing, I highly recommend AA, NA, addiction counseling, etc.
I also went to some MADD presentations as part of my sentence. Basically people getting up on stage and talking about their loved ones dying as a result of DUI. Pretty awful stuff.
Talk to your mom.. meet your brother down there, have the talk. Bring your mom to a MADD presentation, pretty sure they are everywhere all the time and free. Ask her to join AA/NA and seek therapy for addiction.
Unfortunately unless she is caught in the act it is all voluntary, nothing you can do except ask her to get help. No need to be nice about it. My family told me to get help for years before I finally was required to by the state, so don’t hold your breath.
In a way, getting that DUI was the best thing that ever happened to me, too bad it had to come to that, happy no one got hurt.