Hello and welcome,
No other part of the body as this will give inconsistent results. She needs to use all her fingers alternately and try to prick the side of the top bit rather than the tip. To get more blood, her hands need to be warm. It is a good idea to wash thoroughly in warm water, rinse under running warm water and dry carefully. If she rubs her fingers with her towel this may help, also shaking the hands vigorously and holding them downwards. I also blow on mine at the moment as it is such cold weather.