Is she at risk of an open liquor charge? Would the vehicle be impounded if she was pulled over? What if she had your S with her in the vehicle and was pulled over with the booze in her car?
My dad said recently to me that he thought my W was having an affair. He finally realized that the affair she was having, was with the bottle.
Your W may be drinking WITH someone... then again, based on what you've posted... she could just as easily be drinking by herself...