Take her up on the lizard offer. Research lizards as there are many out there that are good for beginners. You can actually use the lizard as a stepping stone to a snake. I've seen it happen.
Also, try educating her about what you learn about snakes. Sometimes, planting a seed and giving it a little water works much better. Try to get her to go to the expo with you! If you can, you've gained a little headway. If she's amicable enough, you may even get her to hold one. I find most people call them creepy and dangerous because they lack knowledge. Educating her about them can work wonders. Bonus if you can get her to go to the expo with you.
You have to remember, it's her house, therefore it's her rules. It's up to you to find a way to get her to change the rules.

But don't be headstrong with it. Gentle guidance works much better.
Good luck!