@noeuf a lot of people wait until 12 weeks+ to announce to anyone, it isn't unusual and I don't think the OP is wrong for waiting until that point or beyond, it is her pregnancy.
OP I had a similar experience with a family member, the news was told face to face, after being pushed to do that from other family members, it was the wrong thing to do in my situation, the news wasn't welcome received at that point and I was asked not to mention it in front of her nor post anything to my social media, and to basically ignore the fact that I was pregnant with a much longed for child.
I distanced myself slightly, didn't mention the pregnancy unless u was asked about it, and anything I did post (very little as I am private person) was done with the family member blocked from the post, to save feelings.
It did ease towards the end of my pregnancy and under her grief she was happy for me, but wasn't sure how to process it alongside her absolute heartbreak.
Our relationship was strained for a short while, but we are back on track and all I can advise is to take lead from your friend, but please don't feel guilty for your own happiness. Sadly, in life when someone is going through shit, another it sky high with happiness.
Congratulations and I wish you a happy and healthy pregnancy x