I am glad to hear that you have started seeing a therapist. I was also going to suggest going to AA meetings... because as you said whether your mother is drinking or not, the dynamics and pleasing for approval, etc etc dysfunction's still exists.
Getting the help for yourself will help you to manage each of them with more strength and understanding of the situation and hopefully you will be able to set boundaries with your mother.. It is great that you have the professional support and you certainly have the support of us here at the boards.
Please keep us posted.. take care