The newer Apple Time Capsule had no Ethernet port; WiFi only. The campus network does not offer ethernet, only WiFi. Just like a secure corporate WiFi network, access also requires a login, and devices are isolated and can’t communicate with each other. So, there would be no way to connect the Time Capsule to the campus WiFi network and have her MacBook Air access it.

So we the decided that the easiest solution was to use an external drive.

My other child had a similar experience. The campus WiFi signal was weak so we bought a router to connect to the Ethernet port in the room. But the university uses NAC and routers are blocked.