Well, afaik... For people from most countries, I suppose it is fairly doable to stay in Canada up to 6 months.
Longer stay may be trickier / not doable. Maybe it could be easier for underage skaters to get their parents to stay longer, but that does not apply.
This is why my guess is that Zhenya's mom will stay there for a couple of months, until Zhenya has everything sorted out, a place to live, furniture, healthcare and so on, whatever may require some additional support, and then leave.
of course, i am just a common mortal.. but it took me 3 months to switch from province to province healthcare... hopefully they have faster things organized for athletes...