<p>No, that’s not how it works. The parent who claims you as a deduction on their taxes is not the way the custodial parent is determined. In your situation, since you live with both, the custodial parent is the one who contributes the most money to support you. That would be your mother.</p>
<p>If your mom will not make her tax documents available to you to submit for financial aid, then your only options would be to do the taxes yourself as has been suggested, or to explain your situation to the colleges’ financial aid office and throw yourself on their mercy. (Although, if I was you I wouldn’t expect a good outcome from that.)</p>