Take it from me, your thoughts of wanting to have sex with this attractive girl are not irrational. Every guy has them and usually keeps them to himself or jokes about them to friends. It’s normal. In fact joking about seeing this hot chick with friends and wanting to jump in her pants will help you see that every guy has these notions.

What’s irrational is thinking all the negative crap. This girl probably didn’t give you more than a fleeting thought, even if she did notice you.