I agree with what everybody else has said. The best way for her to accept snakes is for her to be informed about them. You can even sit with her at the computer and show her the different morphs and show her how beautiful they can be.

I had the same problem with my Mom, and she loves them now. I talked to her about it and explained that they won't get big enough to harm anything in the house. (I have colubrids right now, but i'll be getting my first BP next week.) Not only that, but they're a lot less maintainence than a cat or dog would be, and significantly less messy. I took my Mom to a local pet store (it wa mom & pop) and let her look at them. Then we went to a local herp show, and she looked at them. Eventually she felt comfortable with that, and let me get my first snake.

Whatever you do, don't buy a snake and bring it in without her permission. It will only end badly. Good luck!