I took essentially celibate to mean they were only with Ouriana. If Camhoinhann became romantically involved with someone else that might break him free from being a furiadhin and lead to his death. I think it is possible that this may be Winloki's part in bringing down Ouriana.
The different furiadhin would seem to have had different motives in becoming attached to Ouriana, a desire for power, authority, greed or fear. I think Camhoinhann's motive was an actual love for her. Hence his nobility and greatness. His downfall of course was in loving a woman who was evil. It would make sense that a woman who is related to Ouriana and perhaps very like she was when he fell in love with her would be the woman who could alter Camhoinhann's attachment to her. What affect this might have on her power I can't tell, although I doubt it is central to her current capabilities. I think if Camhoinhann "betrayed" Ouriana this might drive her even more to dark forces and to become more openly evil perhaps leading others, including her son, to separate themselves from her and this might bring about her downfall.
I wonder which of the furiadhin was the prince's father? It could be Camhoinhann.