Coming out of her health class, louise says to a friend, "i know other people get those kinds of sexually transmitted diseases, but that will not ever happen to me." assuming louise engages in the same kinds of sexual behaviors as others, she is demonstrating:

I would say she is demonstrating denial, that she won't get an STD.

Explanation:

Just because something is rare doesn't mean it won't happen to you, but Louise denies this saying "...but that will not ever happen to me" , but if she engages in similar behavior to her peers, she is exposed to the risk of getting an STD/STI

The illusion of unique invulnerability.