It's not surprising that she has accused you of cheating on her. (And I believe you that you haven't cheated). Alcoholics frequently use tactics like that so they can turn the tables on you and claim they're drinking because of something you are doing. Their drinking problem is never their fault.
Have you tried Alanon? It's been very helpful to many of us on this forum. Also, take a look at the stickies at the top of the forum. They contain lots of good information that you'll find useful over the coming months.