Travis was a man who was physically bigger than her. But what you are failing to see is how she did this by herself: she is fairly tall, and more importantly- she caught him naked, wet, unexpecting her, unarmed, and in a small space. She basically confined her prey where and when he was the most vulnerable. There's no way he could have tackled her, especially not when she had two weapons on her- knife and gun, and possibly a stun gun. From the crime scene pictures she took, I personally think she stun gunned him first to disable him. This is how she accomplished it by herself without help. Her story was that there were two ninjas, since most people would think one person couldn't do it alone.
