Most Helpful Girl
I'm sorry to hear about your mother's death.
She took it a bit far by leaving you over that. If it were me, I'd get annoyed but just tell you not to do it again for your own good. She obviously doesn't want to be with a guy who's irresponsible enough to give into social pressures and take drugs. You can beg as much as you like but if she's intent on not getting back together then you can't change that. However, I do think she took it a little too far which leads me to believe that she didn't really love you that much and she used this situation as an excuse to leave you. That's just my guess so don't believe it to be true.
Send her a message explaining yourself, how much you love her, you're sorry, you won't do it again and you really really want to make things work with her and leave it at that. The silence of you will make her think through what you said and it could change her mind, if she loves you that much.