Hi Nick,
As you pointed out the problem is really with your lack of agreement and change orders. Without seeing your initial agreement and the way your agreement refers to revisions and changes you may be stuck.
Has there ever been any mention to the client that these changes will cost more? For us, as soon as the client asks for something outside of the scope of work, we notify them that there will be additional fees and what those fees will be. Then they can decode if they want to make those changes or not.
In your case, it seems like that conversation and communication is missing, and the sudden emailing of an invoice was not well received. Can you blame them? Unfortunately you may not have any recourse here. You may have to eat the additional fees.
You may be able to calmly explain what the issue is and see if the client may budge and compromise with some of the outstanding fees. My thinking is that she will not. Sorry I can’t offer a magical solution.
I d suggest that you do not turn off the dev site. That will get ugly fast!
Best of luck tomorrow!
Greg Ball, President
Ball Media Innovations, Inc.
https://www.ballmediainnovations.com