Convince her to let you get a cute lizard "instead". Something with personality like a beardie. They make great pets, and you might find you really like them a lot once you have one. But more importantly, your mom is more likely to thaw towards reptiles in general, along with lizards in particular, after seeing how personable they can be, and not at all scary or gross.
I have known many people (usually guys) who were eventually able to get their wives or girlfriends into herps by starting them with leopard geckos or beardies. Maybe it will work with moms too.
After she gets used to the lizard, you can try to work up to a snake. If it doesn't work, at least you will have a great pet lizard, and can get a snake when you finally move out on your own.
Of course, if you don't like lizards, or have zero interest in them, you should not get one just to manipulate mom. But it is hard to imagine how anyone could NOT like a cute little beardie or leo, unless they dislike all reptiles.