As others have said, "This is a Work of Art". Sorry you are going through this. For an artist to do this to another artist there truly has to be some huge reason that she is acting this way. How well do you know her? Have you known this person long? Were you friends before? Did you ask to do this for her or did she ask you? You said that you have a contract, what makes her think that she can get it for less now? Something is really wrong in Denmark (sorry Denmark).
Your work is beyond MAG NIF IT CENT. When I showed my husband the picture all he could said was, "WOW. Then he said, "Keep it if she doesn't pay". We all here have said the same thing. You are worth more than this whole thing. Good Luck on the final outcome, please be sure and let all of us know what happens. Hugs to you. BrendaK