It's your decision to announce your pregnancy the way you want and it wasn't the ex's business to bash you for it. I doubt very much that at 8, your SD would be upset that it was posted on FB. In our case, I told the ex first, asking to not tell the kids until 3 months (in case of a possible misscarriage), we wanted to announce the pregnancy to the kids ourselves, but she told her sons who then told SD (from ex #2), so kids didn't find out from us. Nobody was upset though, except for me and I stopped communicating with the ex, because it's none of her business. So next time, put the ex to her place.
About presents, some kids are just selfish. Example: I made a nice cake for SD's bday with raspberries, just the way she likes. She even said: wouw, you should open a bakery. 2 weeks later, I made a cake for SS's bday. It was actually a simpler cake, but what do I hear? "Oh, it's better than mine!". Kids seems to compare and want things they don't get, it doesn't feel good when you spent time thinking of them, but it's just like that. Just forget it, it passed. And it's not the ex's business what you do in your house, unless there's abuse.
It does sound that she's influenced by her mother. My DP has 3 children and all of them were excited. if the mother has an issue and expresses it to the child, chances are that the child will have an issue too. It happened to me in my previous relationship. My former SS was asking to have a little brother, but when my son was born, his mother went crazy and his attitude changed too.
I say, talk to your SD, reassure her, maybe you can read educational articles on the internet....Don't pay attention to the ex, let your DH deal with her and take care of yourself. Posters here only tell you to think about others, but you also need to think about yourself. You have the right to have a child.
There's something magical about pregnancy and birth that affects people around us, positively or negatively, at some point things will calm down.