OK Let me try. Assume and prepare that your RA will relapse. That way when they do, you won't be angry. And you also will react from a more calm place.
Just because AA says they can start over, doesn't mean you have to. If they relapse, be prepared to calmly be apart from the drama. Go and sleep in the other side of the house. Get out of the house with kids if need be. But do so calmly.
If he/she is verbally abusive or baiting you verbally (very common), don't engage them. You simply let it go, walk away and implement your plan to distance yourself.
Further, don't believe what they are saying, only what you see them doing. This will initially enrage them and typically you will want engage in that anger. Which is exactly what they want. DRAMA and CHAOS is their friend, not yours.
You treat it as a sickness by NOT CATCHING IT YOURSELF.
Be better then the are, stay above them and the drinking.
It will take time to learn to turn away from them, but it saved me, kept me sane, calm and level headed. Which serves you better then it serves them.
I called it Me Time. And I learned to take a TON of it. My ex would drink, I'd be gone as soon as I knew it. She felt like she could punish me by drinking more. And I learned to not give that a second thought if she did.
At least one of us stayed sane in the process.