Treasure was coaching herself aloud on foot position and shoulder movement while delivering her blows in our session. She is untrained and could injure you without intending to do so, or on purpose.
It is much better to go with a black belt in a martial art that teaches striking, as they will be safer and more effective at punching. Brigita is terrific at it, and you don't have to just let her do it: You can try to defend your stomach and she will target your head with light taps until you raise your guard. She will also deliver some effective kicks to the stomach. She'll beat you for real unless you have some advanced training yourself.
Jennie Vaughn is another good option. Less power in her punches, but she will hit whatever target she chooses to. I think her black belt is in Tae Kwan Do.