@KinkyFriedChicken - Yes, like Kawaii Punkd said, don't let other people turn you away from your passion. If it makes you happy, who cares if other people (even your parents) disagree? Mind you, I didn't start cosplaying until I was in my 20s and out of the house, but I remember as a teenager my parents constantly griped about my love of anime - Sailor Moon and Pokemon in particular. I was always drawing Sailor Moon fanart, and they wanted me to pursue more traditional art styles, such as oil painting. I still remember the day they stopped bugging me about my fanart, too... I'd drawn a picture of Eternal Sailor Pluto I was very proud of, and showed it to my sister (who loved my fanart). Without a word, she took it and showed my parents. They never bugged me about my fanart again. I think they saw how my love for the show was improving my skills in drawing.
Today, I earn my living as an artist, and my parents are always asking to see pictures of my cosplays, and have themselves become Pokemon fanatics (oh, how evilly I cackle). It might take time, but if your mother sees how happy it makes you, eventually she'll support your hobby. Even if she finds it a little weird... because let's face it, everyone's weird in their own way.