Hopeful that is such a tough one. I feel like if it finally happens for me, I'll keep it fairly quiet until it becomes glaringly obvious because I'd be so terrified that something could still go wrong. Also, none of my friends are in a position to want to TTC yet anyway so I wouldn't have to worry about upsetting anyone.
Like you, I prefer to be able to react however I want without the pressure of having to put on a face in front of other people. DH's friend recently announced (by text) that his girlfriend of a few months was pregnant and I just went into the bedroom and sobbed.
I'm really struggling to work out what's best in this situation. I think as she is one of your best friends, telling her in person would be favourable. As long as long it was in the privacy of one of your homes and she (and probably you too!) could cry and do whatever they wanted to. I feel as though if it were to be done by text she would immediately know that you felt apprehensive about saying it, and then probably feel guilty that you feel that way.
I know that was really rambly, I keep coming up with different answers and then deleting them! Looking forward to reading what others have to say! x