Still don't understand why so many people wanted to migrate to USA. It is not a country where your dreams come true, it is a country where your dreams turn sour.
I'm surprised that she was so nonchalant before entering the building. In the same situation, I'd be on high alert for any weirdos and their path of travel. As long as she was in the middle of the street, the guy was unlikely to attack because it would be too public. But when she headed indoors, there's some screening from attention going on. He seemed to be pacing himself to get to her room door just as she was going in. Nasty customer and quite well-practiced too.
Needless to say that guy was pretty fit and tough enough. Even if you fight him off, you're still going to be suffering from the physical trauma from delivering and receiving blows. There's nothing for it but to run into the room and call 911. Pepper spray and alarm/yelling is the next best thing.