Some tips:
_ To make the girl earn/lose money fast, go to the black suit guy in front of the theater (in the pic) to "check what movies are playing today", if there is no movie playing, you can choose a movie to play at the cost 15k C :
. sports movie to make the girl EARN money fast
. horror movie to make the girl LOSE money fast
. youth movie to prevent the girl from appearing in the casino
_ To earn money by yourself fast, play slot machine, try 5-6 rounds on every slot machine to see which one has the most numbers appear usually (there are machines that usually only have 4 or 5 numbers while there are some that have 8 or 9 numbers which will give you higher chance to win).
_ To get seed of story (so that you can know the girl better to duel with her), when the girl appears in the casino, take her to play with you at the tables, there are only the same 4 tables that she can bet with you in each floor, keep playing with her at those tables until you get the stories req .