....Since there is nothing they can do at this point to help bring her back alive; the parents are faced with:
1. Say nothing, which improves the chance her body will not be found in which case their son won’t go to jail forever (and he probably told them he did it bc she upset him so much) and doesn’t hurt Gabby herself because she has already passed.
2. Encourage the son to tell LE where he last saw her (or tell LE themselves), which means the victim’s family gets closure but the son goes to jail.
I am sure they hate that Gabby’s family can’t get closure but, since it won’t bring Gabby back alive, refraining from talking will likely keep the son out of jail. LE will have no idea where to search. Later in time he might give a BS story with a BS place but that is a risk because those stories are so easily proven wrong. Say nothing and then you can’t be proven to be lying.
Or maybe they're in negotiations: location information in return for reduced charges?