Nails
Nothing is haram unless it is qualifies five criteria mentioned in the verse 7:33. According to it, fuhash ( obscenity usurpation, transgression, shirk, and innovation in Deen are haram. Anything that involves any of them above gets haram. Nails pertains to cleanliness. If she can keep her nails clean she can have long nails. But they should not resemble claws of the beasts.