This is the beginning of her declaration of independence, and it's going to last for quite a long while. You job as parents begins to shift from caregiver to direction provider right now.
Tough pill to swallow for many parents, but the sooner you accept that she's never going to be totally dependent on you ever again (barring some horrible accident), the sooner you can get on with the business of incrementally getting her ready for an adulthood full of love, common sense, and good values, which is, really, the true job of parenting. Exerting direct control instead of steering them in the right direction becomes increasingly counter-productive as the years pass, and the smoother you can make the transition (and the sooner you can begin to safely & wisely make it), the better.
This is all hindsight, though. Keep in mind that this might be a lesson learned after the fact for me...