I don't think anyone can answer whether you should tell your mom or not. Only you know your family well enough. I couldn't help but wonder though in reading your post if your mom doesn't already know somewhere in her heart. I can always tell if my bf has been drinking even when I haven't been around him. I can tell by the way he acts and even the way he smells, not just beer breath either but I can smell it on his skin. Could it be your mom already knows but doesn't want to face it yet? Sometimes I confront the bf, sometimes not but 9 times out of 10 I know.