Dear Sad Bouquet,
Your best friend is probably scared. One thing nearly all of my married friends have said is that along with the excitement of this new chapter - the party planning, the dress shopping and the cake trying - comes a little bit of fear.
I know that's not what you asked. You asked where your friend went, and is she staying on whatever strange new planet she seems to currently be straddling. What she needs right now is her best friend. Not the the one who she Instagrammed a month ago saying something like, "In 30 more days I get to marry my best friend!" She needs you.
So first thing's first: a sailing metaphor. When you're sailing, if someone falls overboard, everyone has to stare at the person who fell into the water and point so that he or she doesn't get lost in the ocean. Like an Apple remote in a couch cushion, man, people just disappear. So anyway, eyes on her and the friendship. Don't lose sight, even while she's flailing around and shouting and making you wear an ugly dress. She's swallowing salt water! Cut her a break.
Next, say to her, "Hey best friend. I love you so much and this is all going to be great. I promise. And if you want to talk about anything at all, I'm here." She'll probably be like, "What's wrong? Are you high? I'm fine." Just say it. It's nice to be asked in case she was hoping someone would ask. Be her best friend. You have to help hold this friendship afloat while she's running around with a vocabulary suddenly limited to words like "chiffon" and "endive." What you're doing right here is maintaining the friendship during a time when friendships can strain.
I've seen the Sad Bouquet and the Bride drift apart following weddings. Sad Bouquet pulls away from the Bride because she was bossy and only talked about her imminent nuptials. ( Fuck that word, I know. It's weird to spell.) Bride Best Friend pulls away because Sad Bouquet was being...kinda mean? Or sour. Or seemed unhappy on a day that was supposed to be filled with joy.
I've also seen them come back together, closer than ever. Elastic snap-back depends on how strong the left and right force were to begin with, which means that right now, you need to hang on tight and pull. A little space after the wedding while she gets settled and you get settled will be good. If your friendship is one built upon mutual respect and love, you two will snap back-no doubt about it.
Your best friend will go back to normal once the stress of planning a wedding dissipates. You two will still have long late-night texts analyzing the depths of one another's neuroses. You'll have sleepovers! They just might be "away games," or at your place. She might tell her husband your secrets; she might have already done that? It's annoying, but if she does, it's because she's consulting him as her other best friend to provide you with the best advice. Speaking of, one more piece: Regarding your dress, suck it up and pretend to like it. You get to ruin it on the dance floor.
Ask MR Identity by Madeline Montoya.