Marina's original instinct on the last second shot is right

When she said if she has the open 3, she'd take it.

Generally speaking, if you are down 2, you should almost always go for the 3 point shot.

Consider the general percentages: 3 point shot: 40%, 2 point shot 60% (being generous, assuming you get it in low to a post player). The chance the shot goes in is greater for the 2 point shot, but that get it into OT, not winning the game. Then the game becomes another 50% chance.

So basically:

3 point shot: 40% chance of winning
2 point shot: 60% chance of a 50% chance of winning (IOW, 30% chance of winning).

So the 3 point shot is 40% while the 2 point shot is 30%.