Make sure that you spray them with a curl holder/heat protectant before curling. The hot rollers do work best. The hotter they are (longer they are plugged in before you put them in the hair) the longer they hold the curl. Be sure NOT to exceed an hour of warm up time. The longer they are IN the hair, the longer they hold the curl as well. I leave my hot rollers in until they are completely cool. I get up, plug them in, make coffee, have breakfast, get clothes ready etc. Pop them in, shower, apply face, dress etc, then I take them out on the way to work he he he. When they are out spritz with anti humectant holding spray and should be good.
You may want to look at wet setting her hair. You wash and condition it. Towel dry and apply setting lotion. Comb section to be curled smooth and roll it on appropriate sized curlers (if she is prone to whispies, you may want to invest in end papers also) Set her under a bonnet dryer to completely dry. Wait until the curlers have cooled before removing. Once the curlers are removed, finger style them, dont brush. Put a net over her head on the way to the recital and take it off when she gets there.
I know this sounds way old school, but do you ever wonder how the older ladies in Boca manage to get their hair done ONCE a week in curls? Wet sets lol