I've been on both sides of this, it's hard either way. I would say it kind of depends on if your friend knows you are ttc or not. If she knows you are, then although it'll be hard it will sort of be expected, if you see what I mean. If she doesn't know you are ttc then it might hit a bit harder. Either way I'd say an email could be a good idea because it gives her a chance to digest what you're saying and can go and have a little cry if she wants to, rather than having to force a smile.
My experience has been that with my 1st pregnancy, I didn't even think it might upset someone. I was just so excited after a year of ttc and not telling anyone. Turned out our news was quite upsetting for a friend who was also ttc. I felt really bad about that. Sadly I lost that baby, then I fell pg 3 months later. My friend was still not pg by that time, so I tried really hard to compose a thoughtful, caring email letting her know that however she wanted to handle my news was ok with me. If she wanted space, wanted to talk, whatever. Then I had another miscarriage and I never heard from her. Since I knew she was ttc I had an inkling she was pg so mentally started to prepare myself for her news. When she finally got back in touch, she didn't say she was pg but kept dropping huge hints, and made jokes about pg symptoms (I had told her I was suffering a recurrence in symptoms after my loss) and filled her emails with smiley faces etc. I know she was just over the moon, but since she wasn't admitting the news at this point, I felt it was quite insensitive.
Then my sister fell pregnant as well, and she rang me. I appreciated the call - she told me first out of all friends and family which was so thoughtful of her - but I did start to cry and had to try and cover it up because I didn't want her to feel bad after she had made the effort to tell me first. Also the news was out of the blue as I didn't know she was ttc, so it was a bit of a shock. On reflection I think an email would've been better as it does give you the chance to absorb the news and you can respond when you feel ready.
This is just me though - you all know your friends the best and may have a better idea if they like to communicate via email, face to face, text message etc.
Renee1306 - can you not tell your friend you are ttc because you've agreed to keep it private, or do you mean you just can't bring yourself to tell her? If you and your husband don't mind people knowing you are ttc it might be an idea to bring it up? Just so she will be able to prepare herself mentally for the possibility of you getting pregnant.
Beccaboop I can kind of understand your friend being upset but sounds like she has taken it to a bit of an extreme?! Sounds like she is not dealing with it very well, is she having medical help to get pregnant? Maybe she could use some counselling too if she is really struggling to deal with the pressure of ttc?
Gosh this is really long! Sorry for the essay!! x