Hi, congrats on your pregnancy

Sorry for your sister's and your families loss xox

Maybe she was initially hurt that you weren't the one to tell her and her grief is just adding to her reaction?

Could she feel rejected and/or abandoned by you because you didn't tell her the news yourself? She may already feel alone and distanced by having gone through this experience and not having anyone close who has gone through the same thing?

Were you sparing your own feelings as well by getting your Mother to tell her, so as to not have to deal with her reaction and emotions? I can totally understand how hard it would be to give her that news and I would quite possibly have done the same thing, so there's no judgement from me. Just a suggestion as to how your sister may see it.

I know the loss of a baby/child is hard on entire families, so big hugs to you and I hope it works out for you and your sister xox