My dd1, 13 now, started ballet 11 years ago, aged 2, once a week. It definitely snowballs! She's now 13, doing a baseline 19 & a half hours a week of dance (ballet, tap, modern, jazz, Greek, street, body conditioning and contemporary). It's definitely her passion! I have five children, all four of the oldest ones dance. My 8 year old son has just got into JAs (something I dismissed and didn't even try for with the older ones). He wants to BE Billly Elliot.
My dh was dead against it when I took my oldest to her first lesson, now he's the one playing taxi to her! Getting them to classes, performances and rehearsals, even doing the curtain for the dance school show! Good luck to your dd. I hope she enjoys it.