Jojo is very pretty the way she is right now. She is tiny, large breasts will look wrong on her. IMO she looks completely female already. I can understand her wanting to have large breasts, a lot of flat-chested cis-girls think the same thing but no reputable surgeon would give them breast implants at that age. She's 15! Her mother needs to listen to grandma and tell her daughter "No, wait until you are 18."
And Jazz needs to butt out since it's not her body, not her family, and not her money that will be used for the surgery.