I come from a long line of opionated women (funny how I'm so quiet and shy and all that)....anyways, having dealt with this sort of thing before here's a few things from my personal playbook...
Stay calm. Don't debate because there is nothing to debate here. It's a simple fact that you are an adult, you maintain your own home and in that home YOU set the rules. You would not walk into your mother's home and set rules for her, she cannot walk into yours and set rules for you. That's non-negotiable and not up for discussion. Period. End of story.
You can show respect by not expecting your mother to enjoy your snake hobby. You like snakes, she does not. If you expect her to respect your interest, respect her disinterest. In other words, you can talk about snakes with a lot of people, but not mom. You don't need her permission, but you don't need to be seeking her approval either and you are doing that by expecting her to show interest in your snakes.
It doesn't take much to figure out that this didn't start with those snakes and it's likely an issue that touches a lot of your interactions with your mother. Only you can figure out the relationship you will have with her as an adult dealing with another adult. You'll never change her or control her so you can decide how you deal with her and react to her from an adult/adult mindset not mother/child dynamic. It's quite amazing when dealing with difficult family members that once you change your reactions, they come around quite nicely (or they learn fast where the line in the sand is and how it's not smart to push that line - sometimes on some issues you do have to go there when all else fails).