That sounds like a horrid situation to be in, I'm sorry this is happening to you. I would suggest she is in shock and ignoring that her daughter is sick, however, what I am going to say next is not intended to hurt you or anger you so please don't take it that way. I fail to understand what your mother has to do with the situation. You are 26 according to your profile, and I'm going to assume you're in the UK so I don't understand what her feelings have to do with you getting your meds or not. You are diabetic and if you don't get the treatment you need then you will start to suffer serious complications, and this is the most important thing for you to remember.
I would recommend that you sit down with your mum and google diabetes and the complications arising from it. If she sees what could happen then maybe she'll understand your situation better. If she doesn't, then draw a line under it and ignore her when she says it. Your first priority is yourself. I hope she comes around to understand, she could be a great support.