Alyssa Milano is borderline used badly in all versions, and I have no idea why they throw in the Venkman kiss at the end.
Terminal Reality wrote the character to be Dana Barrett (with her being a descendant of Shandor being TR's explanation for why both Gozer and Vigo went after her), and Sigourney Weaver was approached for the project. Weaver, believing it to be a cheap cash-in, declined, and so the character was rewritten as Dr. Ilyssa Selwyn and Milano was cast. By the time Weaver realized that the original cast were involved, she offered to change her mind and participate, but Milano had already recorded her dialogue, her sequences had been animated and she'd been paid -- it would have been cost-prohibitive to bring Weaver in at that point, since basically all the Ghostbusters would have had to re-record their dialogue, too, and it was already a significantly cash-strapped project.