Here's what I know.
She was on an episode of Law and Order: SVU.
In the episode, there were young girls being manipulated into sexual relations with a man whom they believed was their biological father (through sperm donation/insemination.)
The woman I am looking for was the current wife of the Dr. (the man) who was being accused of the manipulation and the sperm donor.
All I can remember about the woman: English accent of some kind. Reminds me of Rhona Mitra, but Rhona doesn't have any SVU episodes listed in her IMDB filmography.