as everyone is saying, try to be heard.

if that does not work, then go ahead and be "a teenager" as some ppl have phraised it. you are still legally an adult, so it don't matter how you act. you still an adult, and not under her control.

you said that the SS checks have to have her to cash them? what about if you DID have a job. could you cash the paychecks on your own? if so, I'd say get a job, save that money up (in your own account, so she can not get to it) then eventually leave, despite what she has to say about it. without you, chances are she may not get the SS money, possibly going to you. if you still can not cash on your own, save them up anyway til she comes to her senses. I do not know much about the SS legalitys and such, so this may not go quite the same in that light, but the job/leaving should still work.