Lol dude what? All you have to do is give them gifts now and then, and talk to them in their style of belief, If its Morrigan you compliment her alot and when shes with you as long as you do things that benefit yourself, she agrees and approves.
And once you run out of things to say to her thats all you get left, the only way to open new dialog is to improve your relationship with her past friend.
The best ways to do this are, give her the golden mirror, and give her the black grimoir found in the mages tower.