I’ve struggled to explain to my child why we can’t/don’t attend particular non-Catholic Christian churches that we regularly drive by, so I understand what you’re asking. I usually settle for something like, “They worship Jesus differently than we do.” You could probably address many of your daughter’s questions in a similar manner, i.e., “They worship God differently than we do. They do this or that because they are trying to make God happy.” It’ll depend on how old she is, of course, and whether you want to get more specific, but my son is still young so I try to avoid deep theological responses.