I don't think your friend is an alcoholic. You only go out with her once a month, maybe when she's around you she feels safe enough to drink alcohol. If you are worried that she might be an alcoholic you should try and get together in a place where there are no drinks. Maybe you could go to the cinema, where they don't really sell alcohol. If she brings alcohol to the cinema she might have a drinking problem. Or you can ask her friends or co-workers who see her daily, but maybe she will find out and get mad at you. Dealing with people who are addicted to alcohol is very tricky.