More on Ms. Denier here:
https://en.wikipedia.org/wiki/Lydie_Denier
She met Stevens in 1994, and had a serious relationship with him, according to the Malzburg interview, which is just about 8 minutes long.
Her book relates more about their time together and why they did not get married—Steve mentions that, and then asks her to go right to Sept. 2012, so we don’t hear why their relationship ended.
Maybe it ended when he came out of the closet and told her he was homosexual.