FWIIW, many skate techs say once every 40 hours on the ice is typical for figure skaters.
But there is a lot of variation.
Not just by skater, but by the type of ice you skate on. Rough ice, and dirty outdoor ice wear out blade edges a lot faster.
I currently sharpen more often, maybe every 8-15 hours, because I love sharp edges, but I use hand tools (mostly Pro-Filer) that remove a lot less metal than powered machine tools, I think because they reshape the steel somewhat more than remove it - the blades still last me for years, and probably well over 100 sharpenings. But about 30 sharpenings seems roughly right for sharpening using powered machines. Maybe worse if you are still having a bit of trouble centering the blade position on the wheel when sharpening.
Is your daughter old and safety oriented enough to learn to sharpen her own skates? It might encourage her to take good care of her blades. (Or not.
) I've watched a lot of kids run off the ice onto the rubber mats surrounding the rink, and out to the lobby or bathroom, with no concern for their blades, secure in the knowledge that their parents will get them sharpened and replaced as needed. Of course, some adults aren't much more careful.
I've also seen some who don't dry their blades after use, leave their blades in blade guards between uses, or store their skate in a closed bag, box or trunk. All of those increase corrosion and shorten edge and blade life. Hopefully your tool experience means you have explained to your daughter what she should do to preserve her blades as much as she can.