One of the nurses where my cousin works just attempted suicide. I just got a message from our mutual friend that this nurse was caring for 2 elderly sick parents. Apparently she took some pills but they got her to the E.R. in time and now she is in the psych ward.
I found some threads here that come close to addressing your question.
Suicidal thoughts and feelings are not uncommon for caregivers. I don't know of any research, but there may be some. I would think these suicides take place in situation where the caregiver is isolated 24/7 with the person they are caring for. They feel boxed in, isolated and empty of any purpose in life beyond the daily grind of dare giving. Sometimes things get so bad that it turns into a murder suicide.
However for a nurse to become suicidal in a place where others are working must involve more than just the pressure of care giving. I assume this was in some type of a nursing home? Were they her parents?
https://www.agingcare.com/discussions/caregiver-depression-thoughts-of-suicide-142941.htm
https://www.agingcare.com/articles/caregivers-kill-parents-commit-suicide-150336.htm
https://www.agingcare.com/discussions/caregiver-feeling-angry-suicidal-153701.htm
https://www.agingcare.com/questions/caregiver-brother-threatening-suicide-161778.htm
https://www.agingcare.com/questions/caregiver-suicidal-no-support-155622.htm