It isn't canon in the slightest. It was a joke that was played to by Renekton Bot and the other Ahri. it had no real basis in lore at all, really, since Renekton is a being controlled completely by battle-lust and rage, desiring only to cause destruction and kill Nasus. This is your representation of Ahri as you see her, as truthfully to your concept of her being.
I say, if you don't think she should be with Renekton, I certainly can't disagree with you there. You, as the RPer, have the right to make that choice for yourself based on what you think is best for the character you are portraying.