She's a lovely person (sober), good at her job, and good mother (sober). That's what makes it both tough . . . and a shame.
Welcome to the forums. If you've been reading my story recently, you know that my AW just came home from her second rehab a few weeks ago. She's had two bad binge relapses in the following four weeks. When she isn't binging, I find myself thinking EXACTLY what you wrote: sober, she's the wife and mother I always thought she could be.
The irrationality won't change until she wants to change more than she wants to drink. Only she knows when that is, and only you know what your boundaries are and how much rope you have to offer. Opening up with someone outside the family system was a positive step though.