I Have Issues With My Mother

My mother stole £4,000 out of my student loans. When i started University 2 years ago, i was unable to make a bank account. I dont get any post so i was unable to prove my address, and I didnt have any ID, so i couldnt get a bank. I'd been close to my mum, so i asked her if i could use her savings account to put the money while i tried to get the ID and proof of address. 2 years later, I recieved a total of around £12,000 in student loans over the time £2,000 a year i happily gave over to her for board. Then a few days ago i asked her how much i had left. Im moving onto a new course and i have managed to find a bank that doesnt require proof of address. Mostly i left my money alone, only spending it rarely, i managed to spend maybe £2,00 a year, without the £2,000 board each year. Thats around £4,000 pound remaining. Well, when i asked how much was left i got the answer around £200. Which i immediately though i had spent a lot more than i thought. So i went to check, I checked specifically how much i got and wrote down what i had brought and roughly how much it had cost, rounding up each time, then adding an extra £500 for each year incase i missed anything. But it showed the same, £2,000 a year, £4,000 remaining. So i asked her again, and when i reminded her that i know there is more, because when i got my first loan i paid my board and left the rest, for driving lessons. Then she told me she has taken it and that she would pay it back. She is a teaching assistant. Not a high paying job, she wont be able to pay it back.