Well, fitness trackers are meant to be worn on the wrist for accuracy.
Fitbit makes a nice one, here’s a link for kids 8+:
https://amzn.to/331cYWs
But if your friend wants a pendant, necklace, or bracelet, Bellabeat makes one. Note it has features she won’t need now like cycle tracking…
https://amzn.to/2X6tq3Y
See what you think of these two for your friend and Mom! Give her my best, by the way!
🙂