Telling sister who's experienced loss..

So I have lots of older sisters, like 6. This is wonderful because I'm gonna have plenty of help. I've told pretty much all of them that live nearby, except one. We were close growing up, but both are busy with life so we don't talk regularly. Anyways, this is my first pregnancy, and it looks to be going well (fingers crossed). I'm afraid to tell her because she's had multiple losses and even lost one tube and ovary. I don't want to seem insensitive or anything. I'm only 19, so it's going to be hard to swallow anyways.

The rest of my family is quite ecstatic, as I'm already living independently withy fiancé and have stability.

When should I tell her? How do I do it nicely?

I want her to be there for me, because I love her so terribly much, but I don't want her to secretly be angry with me or jealous.