How can i tell my best friend i like her and want to date her if she has a boyfriend?

ok i am in love with my best friend i think i have been for a long time but i just now realized that it's love, but my best friend has a boyfriend i don't think they are made for each other although that's up to them, sometimes when she is talking he says shh so she shuts up, i don't think that is a thing that a boyfriend should do but in fortunately she likes his immature behaviors and still loves him, i can i tell her that i love her and maybe make her fall in love with me, i'm desperate because i love her to much and i hate seeing her with a stupid guy. resuming i want her to drop her boyfriend and be my girlfriend, i know this is a wrong feeling but i can't stop it.