The word “carceral” can be found by a search. (I had to look it up too.) It means pertaining to prison. I am going to take a swing at this and opine that what she is saying is that a decarceral prosecutor is one who opposes sending people to prison.
My feeling on this is that she would try hard not to file charges in the first place, or reduce them if she did, and she would try to keep people from being sent to prison if they were convicted.
I just got home to my 20 Volume Oxford English Dictionary (2nd Edition).
decarceral is not an entry either in the general listing or in the words formed with the prefix
de.
ML/NJ