In this case I don't think the strongest one will win, the clever one will. Medusa will win, because the other two have to fight with their eyes closed. Medusa will make it so the two others will fight eachother while thinking they are fighting her.
In case one of them should open his eyes for a moment, Medusa will be right there to turn him into stone. The other one will notice something changed and automatically open his eyes too, and turn in to stone.

In the end Medusa will win. The other two have changed to stone, or have killed eachother.
There is no other way this can end :)