KindEyes said it best" So.....what can you do for your mother? Nothing unless she asks you to. Why? Because the offering of unsolicited assistance will be met with resistance. But you CAN give her gifts occasionally in the hopes that she'll read them. Books like Melody Beattie's "CoDependent No More" and Naranon literature. If she reads enough of it....she'll start to get it. But that's about all you can do.
In the meantime, as painful as it may be, she will continue to enable your brother and he will continue to use.
Detaching with love is a healthy way to deal with anyone who is addicted. Your brother is addicted to drugs. Your mother is addicted to her son."
My goodness do I know this is difficult.....but it is so true. The only thing you can do to help your mother is NOTHING. Not for now anyway. Trust me, the day will most likely come when she needs you and realizes the extent of her enabling (hopefully); but that appears to be a ways off and you can only do you (so to speak). Let them be. Be relational with your mother, but not particularly intimate, if that makes any sense. I am so sorry you are going through this. But know you are not alone! We understand.