Is it possible to diagnose Narcolepsy with normal orexin levels

I have a 13 yr old girl with hypersomnolence. Her mother has a confirmed diagnosis of narcolepsy (without cataplexy). Her csf hypocretin/orexin levels are however normal. Would it still be possible to make a clinical diagnosis of narcolepsy? Would a trial of modafinil be justified in this case? or would you consider another stimulant?
She is awaiting a polysomnogram/MSLT. Neuroimaging is normal. Normal neurological examination