Spider head, what to do?

Remember my story about the bee attack on the bus?  Well another attack on the bus occurred.  Luckily it wasn't on me, but it was near me.  I'm minding my business, changing the song on my phone, I look up and gasp at what I see before my eyes.  A girl sitting in front of me had a quarter sized white spider crawling around on her black knitted hat!!!  With bugs I don't play, so my first instinct is to find something and kill it.  But then I realize I can't because its on a random girl's head and a sudden whack would likely be offensive.  On top of that, her hat was knit with chunky yarn, so the spider probably wouldn't of died because it's against a soft surface, and it could fall through a hole in the hat and end up in her hair!

So then I thought, I should let her know that there is a spider on her hat.  I played out the scenario in my head:  Me from behind her will tap her shoulder, "Excuse me, not to alarm you, but there's a rather large white spider crawling on your hat." She would immediatly scream, start whacking at her hat, pull the hat off and fling it somewhere.  Meanwhile, me sitting right behind her would end up having the spider get flung on me.  Then all hell would break loose as I scream bloody murder and climb over the people around me who are blocking me in against the window (again) while slapping myself trying to get the spider off of me.  Which would then cause a small bus stampede as the other people on the bus tried to avoid me while I ran around a crowded bus until I felt that there was no more spider on me.  Successfully causing the nuttiest scene that there ever was, on the bus. 

Nope, telling her about the spider on her hat would not be a good idea.

The safest option was to keep my mouth shut and my hands to myself, and hopefully once she got off the bus, someone would help her out.  So I sat there, with that spider too close to my face for comfort, trying not to gasp every time the girl moved her head (and the spider) closer to me.  Then I started getting paranoid about spiders possibly crawling on the chunky knit hat that I was also wearing, and had to resist the urge to snatch my hat off and start shaking it out, to make sure.  While sandwiched between the window and a guy next to me, with my book bag in my lap, I tried to casually reach my arm up brush off my hat.  If there were any spiders I'm sure there would have been a reaction from the people behind me scared I was gonna brush the spider onto them.  So I tried to stay calm.  Paranoia grew.  Just when I was about to ask the guy next to me to let me out so I could move away from the spider, spider girl got up and off the bus.  I was saved!  But I don't know if she was :-/

This brings me to my dilemma.  What should one do in that kind of situation?  I felt bad for not helping the girl be free of spiders.  But I didn't wanna cause a spider induced stampede on a crowded bus.  For all I know she could be someone, unlike myself, who likes bugs.  That spider could have been her spider pet!  She could have got mad at me for having killed the spider for her and cried at the lost of her spider friend.

What would you have done in this kind of situation?  Get the spider off the person or avoid a bigger fit of chaos?

All I know is that if anyone sees any type of creature on me, I give you permission to whack it off of me.  I'd much rather take a whack than be caused to run around like a madwoman because of my scary bug instinct.