She sounds like a full fledged alcoholic to me. She could be using meth, but I don't see many signs in your post. I have some questions that may help solve the riddle. Is she still working? Does she call in "sick" a lot? Is she losing weight? Have her grooming habits changed? Does it seem that everything that once mattered to her, no longer does? How is her appetite?

Small town gossip is just that....gossip. You have been married to the woman for 19 years. Trust your instincts, and look around for more signs. It is not hard to spot an active meth user.