In reply to Mel.

But this was not criticism. Lorde criticism against Lana's lyrics was unjustified in National Anthem song because that track was a criticism against opulence higher class powerful people. Lorde as a songwriter was not able to detect that criticism against opulence. But her criticism regarding is justifiable for Without you song, admittedly.
Lana, because of brutal media & public scrutiny, was having depression & anxiety. She also face problems in her personal life. Nobody in media industry was respecting her.
To prove to herself she started recording her album 'Ultraviolence'.
And during period, lorde insulted lana as irrelevant.
Meaning of irrelevance is that a particular artist's work is wastage & have no any value at all.
Its understandable that LDR will took it personally.
Lorde herself should have thought about it before dissing anybody