I have a alcoholic in my immediate family, dont know what to do?!

Well my dads ex partner who he has 2 boys to 12 and 13, is a alcoholic she has got help a few times but it doesn't last long I posted a question here before about it but since I posted it she has gotten worse.. She isn't trying to hide the fact she's drinking and will blatently go to the shop and buy a bottle of vodka and neck it before she gets back to the house.. She doesn't live with me and my dad n brothers but she comes down everyday .. I have been reading up on alcoholism as a disease but quite frankly it isn't a disease becuase then she isn't taking any responsibility for what she's doing . She's choosing to put that bottle to her lips... I was just thinking would it be a good idea to totally stop her coming down to my home and totally cut of contact with her or would that make her drinking worse? I really don't know what to do my brothers are suffering because of it and I'm getting pretty sick of seeing her looking like death it sounds awful but I wish she would just die because all the argo she has caused our family and what she is doing to them kids, it kills me inside coz I'd hate to see my mum like that ..... But any way isit a good idea to totally cut contact?