I don't think you should get one. If it's going to make her that unhappy, why would you try to force her to accept it? If you keep talking to her about how this or that morph is so cool, and how pretty this one is.. and how much that one costs, wouldn't it be awesome to have one of these.. she might finally decide to show some interest. But if she's insisting that she absolutely doesn't want a snake in the house, you should respect that. It's not MY home, it's OUR home. She has to live there too.
Ultimately you should think about whether it is more important to have her, or a snake. If that's a difficult decision for you to make, you should probably call off the wedding.