Ranran, There's Still Time

Friends, Help Me Find a Post-Apocalyptic Novel Where the Female Lead Can Transform

I once read a novel, but I can't remember whether it was about a post-apocalyptic small world in a quick transmigration story or whether the whole novel was set in the apocalypse. The female lead's power let her transform. She could turn into Sailor Moon, Ultraman, and others. She could transform three times a day and gain the corresponding abilities. I want to reread it now, but I can't find it.