Speaking on the difficulty of maintaining a close friendship with someone as famous as Swift, 27, Lorde told The Guardian, "It's like having a friend with very specific allergies. There are certain places you can't go together. Certain things you can't do.
"There are these different sets of considerations within the friendship. It's like having a friend with an autoimmune disease."
After a fan mentioned how fellow Swift friend Selena Gomez might (who suffers from lupus) feel about the disease comment, Lorde apologised on Twitter, writing, " I didn't mention Taylor, but regardless, I f***** up. That was really insensitive. I'm sorry. (sic) "