SeatlleDom, as ineperienced as I am, I can tell you to just don't let your fears guide you. You obviously like this sub - and she likes you...When it comes to submission, age and experience hardly counts. My mistress is way younger then me, yet had me submitting to her in a couple of days...
If domination is really natural to you then let that guide you. Use that typical submissive strait to please your dom, to tell him (or her) about your fears, wishes, needs, fantasies etc. It will give her a feeling of safety and grant you knowledge essential for guiding her. As denu tells, a submissive will like and love you all the more for it! Tell us wether or not you met her again!!