I used to know this acquaintance, a friend of a friend from college (I'll call her Denise).  She was awful  - always complaining, never smiled, was kind of mean, and oddly unanimated, like a toy with run-down batteries.

My way of describing her was that she used to be a charming and beautiful girl whom someone loved very dearly.  Then, Denise died an untimely death, and her loved one couldn't bear to part from her, so he buried her in the haunted pet cemetery.  She came back to life alright, but instead of the charming sweet person she used to be, she was what is presently Denise. 

She was a pet cemetery version of a normal person.

If you don't understand what I'm describing, please use this visual guide: