Irene Radford 
Guardian of the Balance [EPUB ebook] 

Caught between her beloved father, the Merlin of Britain, and Arthur Pendragon, the old ways and the new, Wren must find a way to balance the forces of Chaos with peace. She nurtures the land and the people, creating a haven for anyone displaced by the turbulence. And for the safety of all she must guard her heart against the deep love she shares with Arthur, a married king who holds the future of all the Britains in his hands and his sword.