I promised myself That I'd tell my Mum on my terms, when I did, that I'd come to her full of confidence and seemingly happy with myself to give her the best chance of accepting it. I know it's hugely unusual for a parent to be the first person to be told but I honestly figured that in my situation it was for the best (She'd dropped hints that she'd be okay with it before.) she was also the most likely person to not tell anyone else compared with my friends. Anyway, today I ended up telling her. She reacted just as I imagined. She was surprised, but she was completely accepting and said that she supported me no matter what and to not regret telling her. I'm really lucky. The only problem is, I told her when I was drunk. I'm pathetic. I'm sixteen and she twigged as soon as she walked in the door. She guessed what it was I wanted to tell her and it was so easy to say "yes, that's it" that I did.. So now I'm feeling guilty that I didn't tell her with a clear head. I owed it to myself and I'm terrified that soon Im going to regret it. She seems genuinely okay with it though, which is something.
Congrats on getting a very positive reaction from your mother! Don't let the expectation of regret turn into a self-fulfilling prophecy--this is a good thing and should be regarded as such, so take your mother's advice and don't regret it. It's much too late for regret anyway (she's not going to forget this, obviously), so if you're feeling uneasy about the way you came out to your mother, just make sure that you are clear-headed before you come out to others in the future.
Chouchou is right. It doesn't matter how it happened, except that it did and she accepted you. You should give her a big hug the next time you see her.
Oh don't regret it. It would have been better to tell her with a clear head but moms are moms. They know more than we give them credit for. She knows how hard it was for you to tell her. Just be happy that she is fully accepting. You are lucky to have a really cool mom. Congratulations. That's really cool.