How to Tell my Mom about what I did?

[Monica]

I asked my mom a couple of months ago if I could join Twitter. She said I couldn't because there are some inappropriate things on there. I had a dream last night where I joined Twitter and lots of good things kept happening. So this morning, I signed up. I wasn't going to tell here about it, but one of my idols, Cody Simpson, followed me. I am really excited and want to tell her but I can't. She is on Twitter but doesn't know that I am. I feel extremely guilty about the whole thing and want to tell her, but I know that she will be upset with me because I didn't ask her first. What do I do? I definitely want to tell her but I don't know how. What do I tell her, without her getting upset?