I agree that it's hard to come out.
I did and yeah, my parents said it felt like someone had died in the family! They didn't mean to hurt me.

Now, About your friend...
Sorry if i'm mean here, but your friend doesn't seem very nice to me.
If she can't accept you for you, then i don't think she's worth it!
I mean, If she's turned on you, then i don't think she was ever really your true friend!
She could realise what she's doing and wake up to herself, or she might not.
I think you should just wait and see.
Or you could attempt trying to talk to her and make her listen, without the use of violence of course...
Just see how things go.

Now about you're mum...
I too, don't get her logic.
She accepts gays but she hates bi's.
I really don't get that...
She's stumped me on that one...

Well, from experience, if you really want to keep a friend, I would just keep believing that they will come back to their senses. Either you're friend will come to her senses OR she will just be an ignorant little f**ker...
Sorry about that...

I hope i've helped, if i haven't then i'm sorry...

Here's something to say to your friend:
"Why do you hate me now that you know??
You liked me before i told you, and i'm not any different now than I was before i told you!"

I hope that works for ya!!!