My son suffers from neuralgia, and found that gabapentin worked very well for him, so it is sometimes effective. that is a relatively low dose however, about half of the standard PN dosage. She should definitely not take more if she is also taking Lyrica.
There is a lot of information on here about switching from gabapentin to Lyrica, but as far as I know the long term plan is not to take them together. Hopefully someone with more experience with chime in.
Is hers chronic or acute? My son had shingles on his face as a child, so his is post-herpetic neuralgia and the attacks are infrequent. He only takes the gabapentin during an attack, usually brought on by stress.