With girls, our coach likes to have them get
grips after kips at least. Part of this will also depend on their grip strength ( going hand in hand usually with their overall strength ) , size of hand, and swing height.
I put my boys in grips as soon as they have a decent technical swing that is really starting to get big. No hiccups. Also if I see them taking steps in their swing to reduce their swing because they are starting to swing past their grip strength is also an indicator.
Getting back to girls, it will also depend on what they are doing. Basically, if they are grip strong itty bitty, I probably wouldn't have to put her in grips even if she was doing giants.
Some of this also depends on how tough their hands are. Grips are not a cure all for the abuse of bars, but can alleviate it somewhat. I don't particularly care about rips on the base of the hand caused by the grip as this isn't as bad IMO and steps can be taken to deal with it.