There are people that go into psychology because they have issues with mental health.
She may be someone that is OK most of the time, but has occasional episodes that require inpatient treatment.
That she was a patient doesn't rule out that she is high functioning most of the time and trained to work in the mental health field.
I don't think being in the hosptial means anything about what she does for a living when she is healthy enough to work.
Imaginary friends by Bob!