Universal symbols do exist, but in dreams, I think that our own personal associations are more important.
My wife, for instance, loves dolphins, and every time she dreams of them, it is some sort of a lucid dream, with an important message... Do all people dream of dolphins when they have lucid dreams? I doubt it.
Maybe your wife really had some sort of a bad experience with wolfs (like growing up in wilderness, where even if she didn't see them, she was afraid of being attacked). Or maybe, she considers a certain group of people - "wolves", like some people consider certain businessmen "sharks"... It can even be that some people she knows have a last name "wolf" or someone she knows has that nickname, or a company has that word in the name...
Ask her to tell you what are the feelings she feels when she dreams of those wolves, and then to tell you of instances when she felt identical emotions in reality (the first time she felt like that!). That will bring up the real "wolves". It will probably be something from childhood. If she is terrified in the dream, then it probably points to a fobia of some sort, that is affecting her negatively, and that she is not aware of.