Can you really share a Fortress of Solitude?

I actually think that bothered me on occasion, in the CW Supergirl show, where Kara would use her cousin's Fortress of Solitude like she owned the place, especially in episodes where Superman wasn't going to show up. That's probably on me, since I wouldn't be comfortable just letting myself into my sister's house and using her stuff. I certainly wouldn't build my own door to her place, but I would be pissed if she kept a laser gun to destroy me! From 1971, Action Comics #402, "The Feud of the Titans!" Written by Leo Dorfman (credited as Geoff Browne), pencils by Curt Swan, inks by Murphy Anderson.

Superman and Supergirl are destroying U.N. outlawed weapons in the disentegration pit in the Fortress, when they suddenly turn on each other, accusing each other of keeping a weapon to use against them. Supergirl puts her own entrance into the Fortress, and splits the whole place with an impenetratable barrier of super-force. I think I saw that in a episode of I Love Lucy, or maybe Farscape: my side, your side; my side, your side! The fight predictably escalates when Superman starts smashing some of Supergirl's trophies that she left on his side: stop touching my stuff! Make me! Also this issue: the cover story, "This Hostage Must Die!" Written by Leo Dorfman, pencils by Curt Swan, inks by Murphy Anderson. Superman is the hostage here, seemingly powerless against a tribe of "Navarro" Indians, who were furious about the government taking a plateau on their land, "Montezuma's Castle," for a rocket base. "Red Hawk" was a top astro-physicist, which might explain how he's able to disable Superman; but there's more going than meets the eye. The depiction of Native Americans is probably a bit dated, but they come across well: I feel like DC had a few covers like that around that time.