I decided to come out to my best friend. Yesterday evening, I texted her and told her to go to school early to talk but she was late, today we practiced for the school beginning day, when I asked her why she was late, she said there was a traffic jam. And then when I was going to say, my mouth was stiff I can't say anything and I asked her to be at school earlier tomorrow. OMG. That is a big deal with me
I know how you're feeling. I tried three times before I first came out to my best friend. Text them, "I have something very important to tell you. I have been trying to but have been unsuccessful. Next time we hang out, ask me what it is and don't let me leave until I tell you." That's what I texted my best friend and it worked like a charm. He reminded me and gently prodded me until I told him. Good Luck!
It's unreasonable to expect yourself to come out on the first try because it's a scary thing. That happens to lots of people, probably nearly everyone who has come out to people because it's not an easy thing. Sometimes you just don't feel ready in that moment and that's okay, especially since it would have been a kind of spur of the moment thing. It will be easier when you can be alone with her in the morning and she's giving you her full attention - I mean probably still a bit scary but that's normal and you'll get through it. I have a friend who's 1) bisexual and 2) the most accepting, helpful person I know and I still had a hard time telling her. It probably took me a good 3 or 4 times before I could actually bring it up. So don't be hard on yourself. It's completely normal and now she knows you want to tell her something anyway. Once you get it over with, you'll probably look back and wonder why it was so hard. Best of luck!