At the time I just told myself that she latched on to Frank because he was kind to her. I do think it was a thin story, as so much of that period was (even in that story itself, I never bought that Eleni would go into business with Alan-Michael after his scheming and betrayals). There was not much to pick from, sad to say. I remember when watching a particular nadir for me was Buzz having to live in a hovel or something and Nadine had to help him with a mobster and money schemes (I later learned the mobster was played by an actor JFP had worked with on Santa Barbara - I guess that sums up her storytelling choices).
Lucy was not the first example of JFP making her vision the dominant force above any storytelling logic (that would probably be Buzz), but she was the one that bugged me most, mainly because of the timing with Harley leaving, and also because they kept forcing her on Alan-Michael even though viewers never cared. I did start to like her more during the Brent story, but that really was her only strong story even though she was on the show for 3 and a half years.