An addiction is an addiction regardless of what it is. Anything that takes away quality time from the spouse/family/obligations is an addiction. Anything that one chooses over everything else and doesn't see that as a problem is an addiction.
That does not mean that leaving is the answer though. Simply put, this is an issue that needs to be addressed in marriage counseling. If she feels it's a problem and he doesn't but it's coming between them, clearly it IS a problem.
My advice would be to try and talk it out and get a third party (professional counselor) involved. If he won't go, then she can certainly go on her own to learn how to cope and to get advice on what steps she should take from here.
No matter what course of action she takes, it must done carefully and with planning. At minimum, I would get myself to a counselor just to talk it out. There is always something deeper in situations like this. That is not a dig, but the truth.