Daisy my love, I can give no real practical solutions. But can only recommend that you try as hard as you can to build your life, Mum seems to have lost the plot (as a mother myself, I cannot understand that) Your friends will be more understanding than you think.
You could confront her of course, but I feel that you start to accept she has largely detached herself, you will grow into a far wiser person by this horrid episode, though I don`t expect you to believe that.
Take care
M ♥