I think she wanted him because Buffy had him. She wanted to be Buffy, live that kind of life. And Angel was a part of that.
Now, though, I think she feels closer to him than anyone because their paths are the same. He's someone she can relate to, a guiding light for her. He's there to help her on her path to redemption. I don't think she has any romantic feelings for him anymore [I don't think she ever really did in the first place]. I think she just feels a strong kinship because he's done the same things she's done, been to the same place. THE END.