I recall Isabella Rossellini mentioning on a TV talk show meeting
Hepburn in an elevator shortly after Blue Velvet came out. I think
she may have wrote about it in Some of Me. As for Ingrid and
Hepburn, I don't recall any mention of a meet.

Still, some biographers pointed out that Spencer Tracy's brief
affair with Ingrid was the only one Hepburn didn't forgive. This
struck me as odd considering her own relationship with Tracy was an
affair. The Ingrid/Tracy thing most likely happened on the set of
Dr. Jekyll & Mr. Hyde, just before Hepburn and Tracy first worked
together on Woman of the Year.

Did Hepburn see Ingrid as a rival for Tracy's affections? I'm sure
the new bios of Hepburn that are out or coming out soon will no
doubt pounce on this.