As I have 4 attacks per round, was wondering why I was only firing one.
Or, was she throwing 4 fireballs a round?

It's a heavy crossbow, is that maybe the reason?

Does the att/round only apply to melee weapons?

Am I missing a feat, maybe?

This same thing has happened in other battles. They get off a spell after every bolt, but when I close in with a sword, I whack the right number of times.