A relative of mine is currently on probation for her fourth DUI. She has a blow and go on her car but drives her daughters car.

I would get her help. I would have an intervention and check her into a treatment or detox facility.

Call the police, especially when she drives drunk. If you don't, Imagine the scenario where a family friend is struck dead by your family member.... Could you seriously look at yourself in the mirror for the rest of your life knowing you did nothing.
Sad, sort of SCRAM, she likely won't ever stop drinking. So sad.

You have not really asked a legal question. You might counsel her to speak to a lawyer about her course of conduct. She is almost surely going to end up in jail for a long time and have her driving privileges taken complexly away. Anyone experienced in DUI defense can tell her that. The question of what you can do as a family might be better addressed to someone who treats alcohol addiction.

This isn't a legal question, however, this may be a life or death situation and you may want to consider calling the police. She's obviously a danger to herself and to others.

As far as her legal record shows, your relative apparently has an out of control alcohol addiction that requires major medical/mental health intervention--- not so much legal advice. She is seriously earning points for more jail time(which may do her some good). My suggestion to your family try to convince her to get into a long-term alcohol rehabilitation program . Get a mental health and/or alcohol counselor for her immediately. Goodluck.