How can i prove to my mom that i'm responsible enough to have a tarantula?

i've been begging for a tarantula, i know ton about them, i told her they aren't harmless and not to venomous (depending on species), i've written a paper, made a collage, took notes, studyed the normal spiders in my back yard, and even kept track of all the websites i've used. i just don't know why she won't let me have one. i know they kind of freak her out, but i told her they can't ecscape out of their cages and that i probabley won't be handeling it. but i think that she thinks i'm not responsible, so please help me!!!