Are you a 501c3 organization. If so, changing the bylaws could totally change your status and you could lose the tax exemption status.
Bring the subject up at the first PTO meeting. If the answers to your questions do not meet to your satisfaction, attend the school board meeting. At both meetings, clearly state that as a tax exempt organization, the bylaws must be refiled with the IRS and state in order to retain your tax exemption status.
You could report them to the IRS and they would investigate. Since they are to operate in accordance with their bylaws and the IRS has agreed that the bylaws protects the funds from misuse and distribution, they could terminate status.
You also need to have as many parents as possible attend out of concern for the abuse of power and the future of the organziation. If she is willing to have total disregard for bylaws and the members of your organziation, who knows what else she may do.
When you say Admin, what do you mean? Would the town or cities Superintendant of Schools be the Principal's boss? Has this person been approached? Next would usually be the town's School Committee. In my town there are different wards and an elected committee member per each, plus one "at large". These members control much of the school policies and would be a great place to go after the other avenues are expended. What about local papers? This is hardball, yes, but maybe you're to that point.
Lastly, your old Bylaws would have had to of been on file somewhere. Likely at the town hall. I would go there and ask questions such as who governs these Bylaws or school policy.
Ok..this is the deal...
I was on the board last year when we got a new principal. (we all worked very well with the previous principal!) The new principal came in and wanted to take over the PTO. Everything had to be the way she wanted it. When we tried to follow our bylaws she would always say the bylaws needed to be "revisited". Things got so bad that we could hardly function. She would threaten us by saying things like,"If you want to play hardball..." We tried to work with this woman, and when we got nowhere we went to district admin. We were basically told that it's her school and she has control. (Keep in mind that we followed our bylaws and NEVER went against school policy) Things were so bad that 4/5 of us resigned. I stayed on as treasurer so that she could not have control of the money. To make a long story short, she fixed the elections and basically handpicked the people she wanted on the board.
Our bylaws state that our budget is to be approved by the general membership at the first general meeting. Checks (one for $533.00) were written in August before the school year began...out of a budget that was not yet approved. It seems that was ok though, because over the summer the new board (at the request of the principal, I'm sure) went through the bylaws and changed them. They did this without bringing the revisions or amendments to the general membership. This is totally going against the bylaws that were in effect when these people were elected. If it was that easy to just go ahead and change the bylaws without any votes or approval, the previous board could have changed them to say whatever we wanted... Needless to say admin. won't do anything.