I think announcing the marriage on facebook after dating for only a month is a recipe for internet drama.. no two ways around that... it certainly wasn't a smart move on their part.
Years ago I went through something similar with a close female friend of mine.. She was dating this guy that absolutely destroyed her, he had her under her thumb and squashed who she was. They had one of those on-again-off-again relationships, eternal drama, etc. As a friend I couldn't watch this happen and do NOTHING.. I made up a list of a dozen things to do to get herself back.. a few things were talking to some close mutual friends of ours, if not me.. remembering things she enjoyed doing as a kid, and doing them again.. etc. I knew that pushing hard would just make her push back, but I had to offer what I could as help.
About 10 years have gone by since then, we haven't seen much of each other in those years, but we went out for coffee before Christmas, and she said "I really should have listened to you back then, you gave me very good advice even though I didn't follow it, and I really appreciate you sticking around as my friend even when I wasn't being social or friendly... I'm surprised I have any friends left".
I think my jaw dropped. It wasn't easy to say what I had to say, and say it correctly, and I'm glad that it made a difference in the end.
How does this relate to you? Don't take sides on facebook, perhaps tell her personally you don't think the people on FB are right, and they're overstepping their boundaries, they have no authority over her life, and neither do you. But that as a friend you have to say things that aren't easy or pleasant to say and she may do with that what she pleases. If you feel the gods are on your side you might suggest a long engagement at least. (probably best left alone there). Tell her that you're happy that she's found someone that makes her happy, regardless of anything else.
Most of all, keep your wits about you and stay civil!