Say you will be mentioning it on Facebook - then it's up to her if she wants to check your updates regularly or not.
Posted by Chick
Hi hon -
Facebook is a funny one, sometimes it is out of your control.
I haven't put anything on facebook myself about being pregnant. However, just a couple of days ago one of my friends had gotten so used to the idea that they left me a message on there signed: love to you and the bump.
(It isn't a problem at all by the way as it's not a secret etc. However,.).
It did spark a huge wave of 'congratulations', 'ooh I didn't know', 'omg are you pregnant' etc - which I had no control over. (my poor friend was mortified and asked if she accidentally 'outed' me on facebook - bless her!) I'm not a huge talker so lots of people still didn't know (I'm going for the 'they find out when they find out' approach).
It wasn't a problem for me, just keep in mind a lot can happen on facebook in the couple of hours you're off-line
I think it is really sweet you are so thoughtful, it shows you care about your friend and friendship. I would let her know sooner rather than later. I let one of my closest friends know at 9w so she had plenty of time to take it in and make peace. Even though we both know there is still an air of sadness for her around it, she is genuinely lovely about it.
Good luck x