Bianca Andreescu sounds like she has a standard GTA accent, i.e. without the really long A in words like "slams" etc. that you get farther down south in Ontario. And there's no "hoser" in how she talks, yet she still sounds rather distinctively Canadian in a North American context.
What I think is fascinating is that the way she and younger kids in the GTA are speaking shows a development that goes contrary to the received wisdom that the world is homogenizing. Undoubtedly this must have something to do with Toronto now having a stronger sense of being its own centre of gravity.
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Contrast Bianca the GTA kid with a local here from the Stratford area who has a more American way of speaking as typified with the longer A in words like "and."
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You really can hear the difference between the GTA/Golden Horseshoe and southwestern Ontario. But it's devilishly difficult trying to identify any sort of border between the Golden Horseshoe and southwestern Ontario when it comes to accents. I think maybe you can trace an accent continuum along the QEW and the 401 as they proceed towards Hamilton/St. Catharines and London, respectively.