The girl did broke up with the dude 3 years ago (3 MF YEARS), so if both parties (i.e magician dude and pink haired girl) donāt find the whole deal icky(?, I think itās fair game.
Also if she wants to break up whatever relationship sheās in for whatever reason, she can absolutely do that, like wtf people??
And if the white haired guy states to the involved partner that itās a casual thing, itās also fair game