OT - Opinion Needed For Appropriate Response

I lost a twin in my second trimester and had to carry and deliver her.  The WORST thing people could do was to minimize my grief over the loss of the baby.  YES! I was very greatful for my beautiful living little girl, but anyone who has more than one child can attest to the fact that you love all your children no matter if you held them or not.  I had one friend who sent a condolence card with a beautiful bouquet of flowers for the deceased twin and a cute gift for our daughter.  It was the most thoughtful thing I thought.  My husband was bothered by it, but I think men deal differently with these things.  My sister made a donation to the march of dimes in rememberance of our baby and we recieved a card. 
My daughter is now 7 and she talks about her twin and how she will see her in Heaven.  We chose not to name her...I wanted to, but I think that made it too hard for my husband.  So in my heart she has a name, but because her heart stopped prior to 24 weeks, the state doesnt make a birth  or death certificate. 
That is my 2 cents.  Hope it was helpful.

What a sad situation for her.  I agree w/Michelle and Bridget...you definitely need to acknowledge the baby that didn't survive, while at the same time sending congrats regarding the living baby.  After thinking of Bridget's response re sending flowers that will die - possibly reminding of the baby that died - I'd suggest maybe giving a large potted plant - or even a tree - that they can plant in their yard as a remembrance to the baby that didn't survive?  Or is it possible to have a tree planted in a playground with a little plaque 'in rememberance of....' on/near it?

My prayers go out to her and her husband.

Oh, that poor woman. 

I have not read the other responses.

I think you do both.    I would celebrate the surviving twin.   Send condolences for the twin that did not make it.  She will have to bury the twin that did not survive.  So maybe the first gesture is a visit with a card expressing sympathy and then for the funeral a flower arrangement.