Her sister, Inez, was living in San Francisco and exchanging messages about her on Ancestry as recently as 2014. Unfortunately there seems to have been no news since she went missing, despite the family paying for expensive private detectives and offering a $5000 reward. There is also a chapter in a book on books.google which gives more background on her family and touches on her disappearance -
My Footprint
Both her parents are long dead so her sister is her last close relative.
Denise had received psychiatric treatment for depression so, although the family denied the possibility, suicide or cutting all ties for a new life cannot be discounted.
1980022907517_01
More on her personality comes from reports of her disappearance in USF papers (which also note the reward increased to $7000). It states that "As well as being an artist, Denise Dorfman was also an accomplished dancer. She danced in the "Nutcracker Ballet" for the San Francisco Dance Troope last Christmas. She is also a concert pianist. Dorfman also liked to sketch on the beach and near the S.F Marina." It further notes that the private detective retained was Hal Lipset, who was very well known, suggesting no expense was spared in trying to find her.