It's not a bug, just an annoying quirk of neutralize. It doesn't care that she's technically buff immune - due to how the game calculates things, neutralize is checked first. This means that it prevents the buff before her (and other similar champions') buff immunity kicks in to prevent it.The only way to avoid Rintrah's ruptures is to 1) be immune to ability accuracy modification which would prevent neutralize from working, or 2) be immune to the ruptures themselves so that neutralize can't actually do anything.