I think she is too young. It may be something she can work towards in the long term. So if she wants to earn enough trust to do something like this, she MUST call in when you require for eg. She must do this each and every time or back to square one.
This was the deal with my daughter. Look I know you gotta let them go, but it doesn't mean you have to crap your pants all the way through. I explain to Belle that although I do trust her, I worry about situations happening to her, and if she respects the way I feel she will call at the times I ask her to.

I haven't let her venture to the city yet, even though she is 15 and I was in the city with my friends heaps from the age of 13, don't tell her that or I'll never hear the end of it.