Unfortunately I can not offer much advice on motivating your niece because I have never had this experience. I can address your questions about being a pharmacy tech (I was a pharmacist for many years).

I assure you that she will have VERY limited access to any patients in a psych hospital or prison. She will not be put in direct danger, but she needs to use some common sense when working in those types of facilities.

If she does not want to work in that environment look into your local hospitals, they also hire pharmacy techs and pay well. The difference is that there is shift work involved in working in a hospital and likely there is no shift work in the other institutions.