“on her spending 9 months in israel partying.”
You’re right about the finances, but, I doubt anyone’s going to sem to “party” (although you’re allowed to have some fun too, but that’s not the main focus). Just like bochurim need a yeshiva to shteig so do girls. There’s nothing wrong with a girl who doesn’t go to sem, but, it’s a nice year that prepares you for life.