Lorde said she doesn't want to be anybody's opening act, ever. That's why she rejected Katy's request to be her opening act. Lorde's kind of person who stands firm with her principle so I don't see changing her mind about being anybody's opening act even though the person requesting is Taylor.
No Lorde rejected Katy at her first step (she mentioned about beginning or something), opening for Taylor at her second step will be very logical and interesting!
basically calling them out for sending death threats 
to Haylor getting back together.
but damn 
