Future Mother-in-law problem

Do you think this is fair?

I am eighteen, have no parents and share a flat with two other girls. I am getting married at the end of the year to an only son whose parents, naturally worship him. His mother thinks I am going to turn him against her, which is the last thing I want to do as I know what it is like not to have someone to whom you can go when you have problems.

We have been saving very hard to buy our own house and have just enough money left for furniture,so now we cannot have a big wedding as my fiance's mother wanted, but will be getting married in a Register office instead, which we do not mind in the least- no fuss, you see.

Well, my future mother-in-law says that if we get married in a Register office she will never forgive us and will not attend the wedding. When we try to explain to her that we can't afford it she just looks away. But somehow she has managed to convince my fiance that her way is right. She has sent sixty invitations to her friends whom we hardly ever see, and has arranged for a meal at a big hotel, but has not offered to help out with the money side as she says that is nothing to do with her. Do you think this is fair?