She is mentioned mostly in Lies. Katrina is a part of Quinn's fishing group and is human. When the fishing group discovers an odd type of fish Katrina simply says that it's a tuna. It has been also mentioned that she's good with fires, and this skill most likely makes her a crucial part of the group. She also signals to Quinn where the islands are when they're rowing close to them.
Katrina is not known to be a survivor of the FAYZ.