I’m really sorry that your mother let you down by not talking to you- a parent should. But before you wrote that $800 check, where did you think the money would come from?
Do you (or did you) believe that your mother has $40,000 available to write that check? Is it that she has the money & doesn’t want to spend it, or was borrowing always part of the picture?
Did you mother’s plan of the home-state college also involve borrowing? if so, how much?
If borrowing was always part of the picture, does your mother have the financial ability to co-sign for a $35,000 loan for you?
If not, it really doesn’t matter what you want or what is reasonable or what is responsible: the dream school is a mirage. It is not real for you.
And, taking nothing away from the very real pain of seeing a dream go up in smoke, the pain of going there for a year and then having to leave to move back home is exponentially worse.
Happily, almost every college / university has a strong biology department, and you don’t need a name-brand college to get into dental school. What you do need are top grades and test scores- and the ability to pay for it (the cheapest dental school is approx $150,000).
So go back to basics: figure out what your budget is. Have that talk with your mother. Come back with a budget, stats & state & people here will help you find options.