If Celeste had voiced that concern over a de Dannan, Avna probably would have smacked her. It was a de Dannan; the worst he could do to her was flirt.
"Let's say it is the same one. Does he know who this Demon is and just has not been able to locate him?" If it was the same Demon, she needed to find this Tristan. Both to help her find this asshole and she'd be damned if she let a de Dannan take him down without her getting in her fair share of revenge.