I've read that a few people are being rubbed wrong by your 'she was a serial dater' comment. I don't think it was malicious, you were just saying that this relationship is even more intense and exciting for Sarah. At least that's how I took it.

I can understand why Sarah was rubbed wrong--only in the way that she wanted to find fun collaborative things to involve both you and her being in the spotlight, and it hasn't happened.

However I don't think it's wrong AT ALL that you went the private route with the announcement or the mothers day gift. The announcement didn't end well but that wasn't it at all, you did it beforehand so she could have her time in the light when she told it, being the central focus. I'm really surprised that people are assuming so poorly of you. Also, you had a right to give your mom the gift, you once again tried to casually give it out of the way and not flaunt it. If you had maybe suggested to Sarah that she could get your mother a 'mother of the bride' shirt or whatever, so that Sarah could have felt like she had her own extra thing. (seriously though, it was mothers day and you're gonna be a new mother)

Once again, Sarah is being a bit ridiculous but I think she did try to reach out a bit with the asking to do joint things.

I think if you know Sarah won't be the one to initiate contact, send her a message, tell her you're sorry it's felt like you've been trying to one up her, you thought keeping the stuff private would take less attention away from her time. It's an exciting time for both of you and you should suggest helping her think of little things to celebrate her engagement as other users have suggested.

Sorry this is going on :c, I hope you two can reconnect soon and both of you can feel special.