samarm, it’s not that unusual. It’s a sign the machinery is in good working order.
As a woman, how would I react? Well, it does depend somewhat on the guy. I mean, I’ve had male friends with whom I’ve had no romantic/sexual relationship get boners in my presence. As long as they’re gentlemen about it, it IS flattering, especially the older I get.
Being a gentleman, of course, means not making a move on a platonic friend just because you sport wood. Now, if you ARE in a romantic relationship that might be “rearranging the package” if you’re in public to adjourning to a private place to make use of the boner.
Seriously, though, we women do understand that a man’s penis is a somewhat independent organism, not entirely under the man’s concious control. In fact, we often find the penis a source of amusement, although mom taught me at a young age that it’s not polite to point and giggle at them.