I strive not to relapse when my son does. Easier said than done.
You thought she was on the path to recovery and then this incident. But this does not mean she is not still on the path to recovery. She is going to take the long road like most addicts do. Relapse is a symptom of the disease.
As she figures out her next move, she may bounce back quickly.
I hope you bounce back quickly tto, so that your happiness is not dependent on her sobriety.