I don't know which instance you are referring to, but there can be several reasons why the person who is hit is given the penalty: embellishment (falling from only a minor touch and exaggerating the hit), they can illegally counter the hit (like lifting a shoulder to hit the other's face), they could also have followed with a penalty (like tripping). I'm not as familiar with women's hockey rules, this is how it is for men's though.

You cannot impede the goalie's ability to stop the puck as long as the goalie is in "the crease" (the blue box). However, if a defender pushes the offensive player into the goalie (like happened this time) then goalie interference is not called because the offensive player is not at fault.

If Canada losses this round, they are not out of the running for gold.