It's interesting that she separated from her husband in 1989 and he has spoken with police and appears to be a witness, not a suspect. Her remains were not thought have been there as far back as 1989, so it sounds like she moved on and was in another relationship.
Hopefully her family (or maybe even her estranged husband) might have some idea of who she was dating closer to the time of her death, as it sounds like whoever that was would probably be a suspect or of interest to LE as it's suspicious she was pregnant and then found dead. Yes, it could have been anyone who killed her without knowing more about the circumstances..but. I wonder if they ever tried to get DNA from the fetal remains as she was 6 months pregnant at the time of her death. That would reveal the father, who may or may not have more knowledge of how she ended up dead in a flooded basement.