I would leave her where she is...you don't want to confuse her now. And though 15 minutes away isn't far, if she has decided that your pond is "home" she will travel the distance to return there, adding more dangers in her path. You've done the right thing, now is the hardest part....leave her...
You did the right thing!!!! And don't ever let ANYONE tell you different! A wild duck is meant to be wild, no matter what circumstances fall in their way. Congratulations to you on your successful release!!