I wouldn't put anything on the application. If she is asked in a job interview about gaps in employment, she can say that she had an illness. She doesn't have to be specific as to what kind of illness. I've had a similar issue because I missed a lot of sick days on my last job because of depression. When asked about my attendance at my last job, I will just say that I was sick or ill, I don't need to tell them it was depression. Too many people are biased when it comes to mental illness/addiction.