Hi,
I'm in no way an expert, so you'd need to verify the following yourself, but I think .....
I haven't looked into it for a while, but there are insurance policies which, broadly speaking, I think they term 'backpacker' policies. They are designed for, as you might guess, backpackers doing a few months/a year of travelling. I'm not sure if they are open to all ages, you'd need to look into that (perhaps they legally have to be?).
There is a company, World Nomads, they do these kind of policies. Have never used them, don't know much about them, but it might be a starting point.
Hope this helps and hope she enjoys the wedding!
Cormac