The 22-year-old singer met William and Kate as they visited Charlottetown, in Prince Edward Island a part of their royal tour of Canada.
In a bizarre outburst Ms Blanchard thanked the 'douche' for his visit before adding: “I can't believe that just happened.”
Prince William and Kate reportedly laughed off the gaffe.
Meaghan Blanchard's second album, 'Chasin’ Lonely Again', wonthe 2011 East Coast Music Award for country album of the year.
Much chastened after the gig Ms Blanchard said: “It's an amazing opportunity. I feel really, really, really blessed.”
The urbandictionary.com defines the word 'douche' as 'A word to describe an individual who has shown themself to be very brainless in one way or another, thus comparing them to the cleansing product for vaginas.'