TBH if I were in your sister shoes I would feel exactly the same way she does. Well I have no idea what it would feel like as I haven't had a stillborn baby but I think I would feel how she does. I personally would want space from my pregnant sister and not want to see you or speak to you unless it was on my terms. To me it would be a constant reminder of what you have and I'd assume if I were in your sisters shoes got so easily and what I didn't have. I imagine the hurt would be soul shattering regardless of weather she knew you were trying or not. If she knew you were trying she probably has been worried about an announcement for sometime and if she didn't then it would probably be a huge shock.

I HATED my best friend when she announced she was going to try for a baby and then a month later when she fell pregnant just after I lost an early pregnancy after 2yrs trying. I did not expect her to not try but I guess at the same time I wanted to be first as I was trying so long and in my eyes it was my turn. It was a real kick in the guts every moment I thought of her, saw her status of facebook etc. I rarely spoke to her for the duration of her pregnancy. I couldn't imagine how I would feel if I had lost my baby in the 3rd trimester that was just after a m/c and infertility.

I wouldn't write her anything other then say how sorry you are that things have turned out this way or get your mum to remind her. For me (and I know everyone is different) I'd ask your mum to say I had no idea what she was going through, your sorry for her hurt and you love her and will be their when she is ready. That maybe a week or years away. If she has said she wants not to speak or see you I'd respect those wishes. I would however tell your mother how you feel and the lack of support from your family.

I agree with Junglemum that your mum probably feels your sister needs her the most so is giving her all the support she can. I don't think its that she would mean to make you miss out but perhaps by giving you support its fueling your sisters pain.

CONGRATULATIONS on your pregnancy. I'm sorry your whole family has been through such a tragedy which has put a dampener on what should be a very exciting time in all of your lives.