The 1992 world of computers and networks was much different than our world today. The author uses the analogy of familiarity with a browser and gaining access to a gmail account. I remember 1992. I remember the systems that didn't have lock screens, and didn't have log in passwords. Couple that with a theme park's computer system that's still being built and debugged.
I think it's totally rational that a kid who's familiar with a unix filesystem and a navigator could poke around a system until she found some security scripts.
I take much more issue with the "video feed" of the Dock with the worker Nedry was talking to - and the video playback bar on the bottom of the window.