After the End: Undead Fear: After the End Series: Book 1 (Paperback) (ISBN-13: 9798232749897)

Rule One: Nowhere is safe, only safer.
Rule Two: People will do insane things to survive, so trust no one.
In a walled city at the end of the world, with zombies shambling everywhere, Gwen has a choice. Stay in a place where things are mostly safe, but is probably going to fall. Or go out on her own again.
Surviving the zombies is something she knows, something she's good at. It's just too bad other survivors make the surviving part so damn hard.