The cold hardy duck

I am a rookie duck owner, I had my first chickens this summer and because I wouldn't be able to heat their coop they are now in my freezer... I had an empty coop and found myself adopting a friends lone duck (she looks like a mallard but is a domestic duck purchased from TSC) when he no longer wanted her. I agreed only because I researched that ducks are supposedly cold hardy. I am in southwest ontario and winters easily stay at -15C without the windchill (down to -30 with windchill). My little duck is in a 3x4 coop of reclaimed fence wood and 2x4s. It is off the ground by about 2.5 feet, east facing and the door is shut each night when she goes to bed. I stuffed all the summer vents with old t-shirts and screwed plywood over the windows. It is full of straw and I bring out water and food each night when I shut her in. She has a pool with a windbreaker and livestock weighted heater she can hang out in during the day. I just worry that she will be chilly all by herself and wonder if I should put her in a crate in my garage at night for warmth... Thoughts? Recommendations?