This post might be a little late, but I just wanted to say don't give up!
Have you tried different nursing positions on that side? Sometimes the football hold is easier to get a good latch with. You can also try nursing laying down.
Are you sure it's the latch, or could it be a nipple 'bleb' (like a white pimple-type thing), or thrush? Those can both cause extreme pain. Does the nipple look normal when she unlatches, or is it 'lipstick' shaped?