I personally wouldn't recommend trimming and/or filing that much beak away. From the looks of the photos, it seems as though cutting or filing that far would make contact with blood vessels and nerves, which would be a very painful and messy experience for you and your bird.
If you don't have any special attachment to the bird, I would cull her, especially if you plan on breeding any of your chickens. However, if she's more of a pet than anything and you don't plan on hatching chicks from her, I'm pretty sure there's a special "club" of sorts somewhere here on BYC for owners of crossbeaks. It gives feeding tips and other helpful information on how to make your crossbeak's life as normal as possible.
~Gresh~