You are not obligated to have anyone in your life who makes you miserable.
Your mother has the right to live her life the way she chooses, even if you don't agree with or even understand her choices; that's a truth all families of addicts struggle to accept and wrap their heads around. The bright side is that you have the same right. Life is too short to spend it waiting for others to see what their choices are costing them. You have an opportunity to be an example to the rest of your family on how to live the kind of life that doesn't involve constant manipulation, secrecy, and denial. It just might not include them, unless it's on your terms.
Sending you strength and courage.