This is easy to say because this wasn't my girl, but, here goes.....I feel for you, but you still have your lovely girl, hogged or not she's still the same girl. Don't try to repair with mane wigs, even if its her own hair, you'll always know when you look at the photos.
and don't forget - this is just a cosmetic thing - for now, however upsetting xxx.
I think you've handled this brilliantly - by not flying off the handle and being understanding that this girl made a mistake.
I can imagine how easy it would have been to go mad/burst into tears - so glass of wine and choccies for you!!
Why not set it as a challenge to your photographer? The pictures are a memory, so why not get some really arty ones as well as normal? The lack of mane won't matter then and you'll know shes your girl.
Whether the shots taken are classic and 'normal' or arty- it will still be her in the photos The mane is so cosmetic