Some say that the only difference between her and the patients is that she has keys to come and go.
She has been at the hospital so long that she qualifies for retirement under their old pension system, which is now defunct, but she is grandfathered in. She ranted for weeks about how she put in for retirement and the people who handle the pension said she was short one year of service because of all of her Leaves of Absence. She took another Leave, explaining, "I'll show them. I'll finish out my remaining year on Leave." After a three month absence, she is back, angrier and nastier than ever. Someone clued her in that going back on Leave does not satisfy the deficient year of service.
It's more like a punishment to those who have to deal with her every day.