With my second pregnancy we told DS at 12 weeks before we told anyone else (besides my mum who knew right away...and blabbed to my dad). I'm glad we told him even though we had a 2nd tri loss, as at least he knew why Mumma was in the hospital.
With DD we waited though, until 18 weeks, then told DS then everyone else (except my parents, who knew again). DH's fam was told at 19wks, extended fam at 20wks. No one hassled us about it, they were all really excited.
Part of our delay was due to the loss but in part it was because with our 2nd DS asked everyday after he found out whether the baby was ready yet. My parents live 5 doors down, helped care for DS during our loss and would never dream of telling anyone until we gave the go ahead, so we were comfortable with them knowing.
With DD's name (similar situation as we weren't telling until birth), DS did know and totally blabbed to everyone but most ppl didn't catch on and DH and I just pretended he didn't say anything.
Moral of my story, whenever you are comfortable with her and everyone else knowing.