Their relationship is quite fascinating to be honest. There is Madonna, biggest popstar on earth, probably aware of this UK based female making big waves in mainly European and Australian markets during the late 80s and 90s, yet only finally acknowledging her in 2000 at the VMAs. Then she experienced Kylie's early 00s imperial phase while a resident in London and right after her cancer battle which must have felt quite personal. I remember reading she was attending Kylie's tours, too. Out of all her surviving peers I think she admires Kylie the most not just because of the artistry but also Kylie being so strong. People say Madonna and Kylie are so different but ultimately they're quite similar.