well actually CARRIE is the one in love with Mr. Big, and in the movie though she is devastated at first she does restart her life and is happy -though she still is in love with Big and would be happier if she were with him. However I don't think it has anything do to with needing a man, it's wanting to be with the person you love; if she wasn't in love with him she wouldn't want to be with him.

The movie actually proves the opposite of your point when it came to Samantha's story line, she is in love with Smith but she wasn't willing to make the sacrafices that needed to be made in order to be with him (staying in LA and living his life) so she left.