Hi nicolemariee,
I'm really sorry to hear about your mother. I know this situation you find yourself in is really difficult to understand at the moment but you are not the only person to have to go through it. Have any of your friends parents gone through anything similar?
You said that your mum get's angry quickly. I would recommend not talking to her at the moment. She's in a very selfish place at the moment and her anger would be directed at you as someone who wants to stop her fun.

A councillor at school should be confidential and it shouldn't get back to your mum that you've gone to see them. I can understand your reluctance though and you cannot be 100% sure that it wont get back to her in some way.

Although I'm not a religious person, how about talking to a priest or similar (maybe a female one if one is in your area). I don't know where you live or what your religion is, but you should at least be able to tell them how you feel to get these feelings out. They will probably also be aware of other services that may be available to help you. You could pop along to a service on a Sunday and as they greet or goodbye people, ask if you could talk to them.