Is your guinea pig eating normally? Is her weight stable? If so, I wouldn't rush into doing anything. It will be worth checking around for a good, guinea pig savvy vet and then getting them to check her teeth. The wear of the incisors is unusual, but as long as she's eating well and maintaining weight, this could resolve, without treatment needed. However, if her weight is dropping, then step in with syringe feeding, whilst you find an experienced dental vet.