Davih said:
It's not an unreasonable request, really.
For starters, if you total up the support you've been provided over the years, can you really still say she "owes" you money? I mean, I know about the idea of paying your debts and all, but when you're 14 and you give your mom money, you're helping the household. It's not a loan.
And if you're still living at home, it's incurring expenses. Yet, as you've mentioned, she's not taking in the same amount of money now. She's having to meet the same expenses with less money.
Before you talk about how she's too lazy to get a job, also consider that you're accepting government money to go to school. You could be in a situation in which you have to work a full-time job to get through school
and still have mountains of debt. Your mom may have her faults, but this particular request is not automatically unreasonable just because of her circumstances.
If you choose to live at home when you
could be living on your own, anything less than
real rent payments is a tremendous favor. You have an out, though. You can move out and try things on your own. But don't try to rationalize away the very reasonable claim that you contribute financially to the household in which you're living as an adult.