She's tough! She's a harbor chiiiick!
I would say there's no evidence to say she couldn't do a lot of things or that they didn't take out traffic lights. Probably just not essential to see everything happen. Yes the movie reason and surely the easy way is not show it because it would cost money and the fact that she stays in the same position. I think if the vibrations wouldn't shake her to pieces, it would have been damn hilarious, thinking about her running down the street.
Well maybe funny in a "good thing they didn't do that" way.
Somewhat on topic, I still love the sight from inside the museum, the slime uncovering the skylight and that head peeking in. "WHAT? NOOO! GO AWAY FROM HERE!"
That entrance was I thought one of the cool things about GB2. A lot of people hated the Statue of Liberty in the movie I know but I thought it was kinda elegant and symbolic, while being really funny. Only these guys would think to do something as ridiculous as moving a national monument down the streets. Let alone with an NES Advantage
Other than the whole "end of the world" setup on Venkman's show, when I was a little older I appreciated the other things that sort of tied in the slime and Libby. The beginning, Egon and Ray wondering if human emotions actually affect the physical environment, seeing the angry people on the street at the beginning, showing how a toaster could move and then later how we would see that same principle in effect. A lot of people knock GB2 for a lot of reasons that I can see but I think the writing was pretty good in those elements.