Adult child wedding

You say she "put something on Facebook", but what exactly did she put? DS and his lovely DP are "talking" about marriage, but they're a million miles from any definite planning.

How adult? Because young adults can be pretty self obsessed still.

It's shitty but the best thing to do is talk to them and don't play any games or anything, just be straightforward. Sets the tone.

Surely that will come off as passive aggressive
I'd just ask, don't make it about you
I'm hurt. I'm sad. I should have known. I am disappointed. I feel let down.

More like is there a reason you didn't want to say? I would love to have a lovely relationship with you, if you are unhappy please let me know so I can fix it
I am really happy you're happy, congratulations etc

Oh dear, that's awful. I know that young people tend to use social media for this sort of thing, but I'd still expect a personal message from my daughter. You must be feeling awful. But I wouldn't stay silent - if it's been three weeks since you found out, I'd suggest that you should ring her and say ( in a light way) Oh I was pleased to see that you and Mr X are going to be married - how lovely ! And then see what she says.

I'm assuming that you normally get on well with your DD . If there is a problem between you, that might explain why she didn't mention it. But in any case, keep smiling and keep communications friendly. It won't serve any purpose to show any animosity about her announcement.