Unfortunately this happens all the time. I know a friend who wants to breed hers and she is too small also. But you try and try to tell them but in the end they are going to do whatever they want no matter what you say.
I know how you feel, like the situation is hopeless. They refuse to listen but in the end they are going to be the ones who wish they would have listened. It is so sad that they won't listen and have to learn this the hard way.