User blog comment:Real Godisme/Chapter 481/@comment-26389992-20160412012108/@comment-7418318-20160412084337

They might have been friends once, but toward the end of the Tenrou arc, when he caught her betraying Grimoire Heart that friendship ended.

He took far too much joy in tormenting her with the truth about Ultear to still be considered her friend. Not to mention that he might even have tried (and likely succeeded) to kill her for the betrayal if that death-wave hadn't slipped out of Zeref.