The next reptile show I know in Ontario is the Toronto Reptile Expo on November 23
The reason why your mother doesn't like snakes should be identified. Is it because she is terrified of them? Finds them slimy? Evil? Depending on her reasons...(maybe she is just worried about diseases?) they can be addressed appropriately. If she has a phobia of snakes, it may be nearly impossible to get her to accept the fact you have a snake in her house. If she is just afriad because she actually knows nothing factual about corn snakes, then presenting her with care sheets, information about corns both in captivity and the wild, etc, may convince her that her fears are based on fiction not fact.
If she is concerned about diseases etc...educating her on common and rare snake diseases, how they don't transmit to humans, and how preventative measures (proper diet, regular cleaning of cage, washing hands after handling the snake etc) can virtually eliminate any risk of disease could convince her to allow you to have a pet.
SHe could be worried that when you graduate from high school in two years and move out to go to college, she wil be stuck with the snake. Some colleges or universities may not allow pets of any type in their residences (though seems to me alot of college students had rodents and reptiles during school when I was in college/university). However, pointing out a corn snake can be kept in a 20 gal tank or sweater box which is really easy to transport (not to mention you can have snakes travel in pillow cases too) could show her that when you move out for school, the snake is easily brought along. Alot more easiler than dogs or cats. Heck, most land lords don't even think to ask if you have a lizard or snake..they may ask about cats or dogs. I just volunteer I do have a small pet but he lives in his cage and doesn't come out. Most landlords are fine with that, as caged animals typicaly do not make noise or messes. Dogs can bark or pee on the rug, cats can pee on the rugs too and meow constantly (especially intact males). Snakes don't bark, pee on the rug (well I am sure they will go on the rug if left on it long enough) or meow etc.
To summarize, find out why your mother doesn't want you to have a snake, then use knowledge and facts to soothe away her objections.