A bangle bracelet is, typically, a solid band that slips over the hand onto the wrist. If she is going to use a lathe she's going to waste a lot of material and make lots of swarf. The usual way is to bend strip metal and solder or weld it closed. I've made lots of bangles out of precious metal (gold, silver, etc), all from strip.
If she wants to use a lathe, then I would suggest a plastic, such as nylon or delrin.