"there was plenty of room for our car to fit in the left lane when we pulled up."

This is where I start to be on the side of the bus driver. She didn't say "the bus was not straddling both lanes", she said there was plenty of room. This indicates to me that the bus was indeed straddling the lanes and the driver of the car thought, "fuck it, I'm gonna pull up anyway, there's 'plenty of room' if I hug the inner line.

My husband asked her what she was thinking and reminded her that a bus driver hit and killed some pedestrians not long ago, but he didn't insult her directly.

I'm with Demonjuice on this one. If you see a large vehicle (bus or semi) straddling two left turn lanes, common sense should tell you not to squeeze in next to it. However, the bus driver should have known the car was there and waited for it to clear. Probably the bus driver should have take up more space of the leftmost lane, because you cannot count on common sense from most drivers, unfortunately. I don't think that drivers' ed classes teach people how to inter-act with large vehicles. I escort oversize loads, and am a retired truck driver, and it never ceases to amaze me what drivers, both car and truck, try to get away with, or are ignorant of the laws. This also applies to some bicycle riders I have observed, and of course pedestrians. I have seen 2 peds this wek crossing intersections against the walk light, and when I pointed this out to one of them, he acted like I was in the wrong.

F 'em. It's a jungle out there.
Another reason to walk (instead of drive) and learn parkour in case some bus be all rollin up on ya business.

Did you get this from Joseph Rose?
Here are the facts:

Buses split lanes, cars try to squeeze in between, and get hit.
That's most likely what happened, I see it every day behind my wheel.

@Davy - if the car pulled up to the light next to a bus that was even a foot over the line, they are BOTH in error and both to blame.

The bus probably didn't move farther left because she needs all the room she can get to make the turn without cutting into the left lane of the cross street. The buses have a long wheelbase, so the side of the bus sweeps across a lot of territory when turning. I don't know if the cross street has a left turn lane or not, but even if there is one, there may have been a vehicle in it. Regardless, the bus driver should have known the car was there, unless the car pulled into the lane just as the light for the turn came on. Then the bus driver may have been looking out for pedestrians and not for some idiot driver trying to pass her on the left.