I'm bi and my mom doesn't accept it. What do I do?

[Vicky]

so i'm bi and like two years ago (i'm 16 now) i told my mom about it, she wasn't exactly mad but she was like "it's just a phase and if you really are what you are you have to know this is not normal" ect. and she also told me i couldn't say a word about it because her image would have suffered or whatever. by the way i was still trying to figure out if i really was bi so i didn't tell anybody about it, but after two years now i'm 150% sure about my sexual orientation and i'd like to come out but i'm too scared. also, today she saw some of my posts on facebook and she called me and told me to delete them because people could have thought that i'm lesbian or bi and she was really mad and told me that until i live in her house i can't be "whatever i am" and she told me she didn't want to hear about that anymore.
but, the fact is that i can't hide it anymore from my friends and i really need to talk with someone about it because i feel like i'm acting and this is driving me crazy (this is probably why i'm writing this, i need someone to know that)
so, what do i do?
i know my friends have an open mind and they would accept me but i just really don't know how to tell them.

P.S. i'm italian so i'm sorry if i made some mistakes writing this
P.P.S. i've just subscribed to this site and i have no idea how this works so i hope i'm doing this right.

i want to thanks everyone who will answer <3