There's really no connection between waxing before u're periods and u're hair growth.. it varies from person to person and their hormones as well.. 12 is still young let her be till she's conscious and ready for it.. no need to fall under pressure :)
Somehow.. start-off with 3 times a week and for the rest of u're regime stick to ctm (cleansing, toning, moisturising) and SUNBLOCK! Can't stress enuff! :) include a multivitamin in u're diet as well..