Sister in law troubles

To start I just want to say that me and my sil haven’t always had the best relationship. She’s always getting upset over things. So 3 years ago when I found out I was pregnant with my son she was so upset because my son would be the first grandson in the family. I totally understood that but at the same time it’s not something that I intentionally did like I mean it just happened. So a few months later she got pregnant and we were all so excited. We all thought she was going to have a girl so we started buying her little girl outfits. Well it turned out she was having a boy and she was bummed out so I decided to try and cheer her up by buying small little gifts that I knew she would like. Well after she gave birth she was breastfeeding and she wanted me to give her my $300 breast pump to which I said I’m sorry but no that ended up in her getting incredibly pissed at me. I worked really hard to buy the breast pump that I wanted I wasn’t going to just give it away and it might seem selfish but it’s true. Fast forward to now I just found out that I’m pregnant with my second child and I’m having a little girl. We haven’t told the family yet because I’m honestly scared of how she’s going to react. She recently said that for her birthday she wanted to go skydiving if she wasn’t pregnant. So I just stayed quiet and looked at my husband like what do I do. I hate confrontation and I don’t want our relationship to suffer because of this but I feel like she’s going to explode. What do I do?!!