Other than my wife, who knew when we first started dating (100 years ago), the first person I told was my doctor. I was so scared, I read my thoughts from a paper I had scribbled my thoughts on. It was hard. Each time gets easier. I'm at about 80 people now. I do have a suggestion, something I used to tell my kids. I gave them a letter telling them that I wanted to tell them something very personal. Also, that I was going to be unfair to them and not tell them right then. I told them what it wasn't (not dying, didn't kill anyone, not splitting up marriage etc.)but I didn't let them ask any questions then. Oh, I said I considered it good news. I let them read it. It gave them a chance to prepare themselves. (Also, it might be a good way to feel your friend out to see if she could keep the secret.)
Anyway, I let it ride for less than a week and then told them. For one thing, they were relieved that it was not something worse. For another thing it made them want to find out the mystery. They essentially decided on their own that they wanted to hear my news. The three of them all said that they would have heard the news no other way. Now, does anyone have any advice for standing up in front of 90 coworkers and telling them? "And now, for my next trick , I'll pull a transgender rabbit out of my hat!" LOL
Good luck, it will be fine!
Moni