When my Cali was a puppy, I had two crates and the xpen set up in different parts of the house so I could always be in sight for her (and vice versa!).
I'm in Aurora, north of Toronto, and we have quite a bit of snow here though probably not as much as you've got in SW Ontario. The temperatures are probably about the same though. The only time I bother with a coat and boots is when Cali goes for a walk since we're out for an extended period of time. She was clipped quite short last time she was groomed so I bought her a coat and we have so much salt on the sidewalks, the boots are a must.
Unless your girl is outside for a long time, I doubt a coat and boots are necessary for the backyard. My Cali was a puppy last winter and although it wasn't quite as snowy as this one, she never seemed bothered by the cold when we were playing in the backyard. She had quite a thick puppy coat then and that, combined with the fact she never moved any slower than a flat-out run, seemed to keep her pretty warm!