I don't have a good answer, but that is what I would expect the girl, and the shop to do.
Does your girl know the extent of the problem trying to exchange the bike? That may sway her a little bit.

The only thing I can think of is... If there is another bike in the shop that your girl would be happy with, the shop may trade you instead of just a straight refund. What brand and exact model is this bike ? Can you post a link? Repainting a new bike is not a very good idea. You have to take everything off the bike,
probably pay more than you think, and the finished job may be less durable than a factory finish.