@lemondrop77, I get your frustration and worry. It’s as if you are having to be the grownup in this situation, but without the information to do so.
So, if I were you I would add up the full cost of the California publics you think you have a chance of being admitted to (including books and fees) and subtract the $5500 yearly amount of student loans you can legally take out for yourself. Let’s call that amount “X”. Guestimate what her income and assets are, try to determine your EFC, and we’ll call that amount “Z.”
Then, the next time your mom withholds monetary information from you (or won’t fill out the FAFSA) and tells you to not worry about it, then say politely “Really? so you’ve saved up enough to pay “X” amount per year for me ? Because that’s what “Cal State Y” costs above above and beyond my student loans without financial aid. And if I’m estimating your income correctly, you might be paying about “Z” amount per year with financial aid but that’s impossible to know without filling out the FAFSA.” If your mom really has no clue how expensive college is these days, maybe the reality of hearing hard numbers will shock her to action.