No she was not! She had quit dating him years before she ran for San Francisco DA, and quit dating him before he was elected as Mayor. And she was a Deputy DA in a smaller California district, not a DA yet, when she had met him and dated him.
The recent interview that I saw with him on the topic, he indicated it was not a sexual relationship, (though that could just be the gentlemanly thing to do, coming from his era?) He said when he met her, he thought she was very bright and enjoyed her younger perspective and her spirit of life all being ahead of her, her interest in solving community problems, and drive to learn the ropes on how to get things done....he enjoyed mentoring her, while he did, and would welcome doing it again.
He also said he did similar to the same with Pelosi, and with Newsome, and Boxer and several others early in their careers and seemed kind of braggadocious about it...