Megan are you still at school and only working part time, if you have left school and work full time, then you should be expected to pay board as we call it here in NZ, at least your share of the food money, just curious as I am not sure on these details.

Don't keep berating yourself for failing to stand up to her, you will find the strength and courage one day to do so, and from that day on I would hope things will take a change in the right direction.

your mother is not stupid, she makes sure she chooses a time when it is difficult for you to say NO.

If you seriously want things to change, only you can do the changing by standing up to her once and for all,until you do that, she will continue to maniuplate you, in a way you are enabling her to continue to do this to you.

I know this is Huge thing for you to undertake, but hopefully there will come a time when you will say to yourself ENOUGH is ENOUGH, I wish you well and hope the time will come sooner rather than later. HUGS.