Unless your bylaws or governing documents give some extraordinary power to your principal, your membership has control of your finances.
I could be more definitive if I were to look at your bylaws.
Who has control over the checkbook? Do you have your own tax ID number? Are you incorporated? Are you a non-profit? There are so many facts you left out of your post that there is no way anyone can answer until you give more information.
Our prinicpa says that she has the final say as to how we, as a school association, use our money. We currently have over $20,000 in our account and have asked several different times to use the money for various projects and she has vetoed us. Can she do that?