Ok, rather than going backwards and forwards I propose to give you an OoC response and then let you lot write around that, including for the NPCs! See, I've clearly got the Anarchy bug

As I may or may not have mentioned before (?!?) she will tell you that the Flowers
always get married on Lyonesse! This is a mythical isle that rose from the waters of the English Channel somewhere towards the South West of England (I think...)... it has a heavy military presence/ cordon (natch) and nobody goes there! So how you might ask...well there's a portal in the astral shallows that you all waded through in your first jaunt in to Below...so won't that be nice?!?

If you want to get really technical they get married on a metaplane that represents Lyonesse...don't say I don't take you to all the fun places! Will borrow heavily from the Court of Shadows sourcebook but it isn't the fey plane! Well...maybe...

Now it is conceivable that you will tell her to rack off but she will point out that for the other Flowers to ratify the marriage it should be done as 'properly' as possible! Now you might argue also that this is being done to bring them back in to balance with the other Houses and they should suck it up...and that is of course your prerogative! As I said, I'm happy for your own creativity to go to town here and come up with some locations that might be fun to take the story to...
So go wild! I'll be sure to make wherever you choose as 'interesting' as possible

As ever I will try and answer OoC questions but no IC from me for the weekend...sorry