WHAT TO DO FOR MY 12 YEAR OLD SISTERS BIRTHDAY PARTY?

Give her money. she seems to want it anyways, so it would be a good gift, because then she could buy something she wants for herself, and you don't have to guess. If you think that's too impersonal get her some cool nose piercings for when she's healed, it would be a fun way to tell her she's getting her nose pierced if she doesn't already know. just like, "Hey we got you some nose piercings." "But my nose isn't pierced" "Well, you haven't gotten your second gift yet,"