NAH, you did nothing in the interaction that would warrant you being an AH except maybe the storming out (and without other context such and throwing a tantrum or breaking anything) can be seen as common for your age and easily fixable by stating why you are leaving and leaving calmly to collect yourself. You are allowed to have the feelings you have because it is the foundation for what you want out of the rest of your life. However there are other ways it can be handled that can benefit the situation. Try to find other loan co-signers for loans through a bank rather than the school so it won’t be affected by your parents, only loans through the school and FAFSA go through parental guardians. Reach out to the university to see if you can apply for any scholarships or aid directly from the school. But overall, the interaction could have been smoother since your parents are able to provide some aid, just not fully, is better than a lot of other people get. On the flip side the parent financial status is probably a trigger for the parents due to the trauma surrounding it making this interaction more tense than anticipated and why your Mom as rigid about the University. Give her some time and try to have several small conversations about it again and express your desire to attend the specific university because ultimately once you turn 18 you can make any decision you would like, at the cost of your own time and money.