I sort of disagree with everyone here... If the sisters were close, of course, talk about it. But also, if you're close, then the pregnant person knows about your struggles and will take them into account, most likely by keeping the announcement to you low-key and asking you how you'd like them to proceed. LW doesn't talk about that part, so either it was edited in the letter, or it didn't happen. And in the later case, well, this is something that should be discussed with a therapist or one's support system, not with the sister.
no subject
If the sisters were close, of course, talk about it.
But also, if you're close, then the pregnant person knows about your struggles and will take them into account, most likely by keeping the announcement to you low-key and asking you how you'd like them to proceed.
LW doesn't talk about that part, so either it was edited in the letter, or it didn't happen. And in the later case, well, this is something that should be discussed with a therapist or one's support system, not with the sister.