get the dragon balls in dragon history on normal level, summon red shynron, look for the symbol that says Z, next to it it'll say new character, wish for it (or chose it) and you have chi-chi!
You have to get the black star dragon balls then summon the red shenron then there will be a list then choose ( Chi-Chi) Character Unlock and then you have her try playing her on Duel mode oh and...