It turns out that Nina Reeves had been married to Dr. Silas Clay (played by the character hopping Michael Easton), who had an affair with Ava Jerome which resulted in her getting pregnant. In an attempt to save their marriage, Nina also wanted to get pregnant with Silas' baby (via Soaps She Knows).
Nina's father had left his entire fortune solely to her. Her mother Madeline Reeves, played by "Knotts Landing" star Donna Mills, wanted to control Nina, thereby controlling the money. When she learned that Nina was pregnant, she gave her an overdose of antidepressants with the intent of causing a miscarriage. The result was not what Madeline was looking for, however, as it only caused Nina to become comatose (via Soaps In Depth).
Madeline eventually told Silas that Nina had died while in the coma (via Soaps She Knows), but in the soap world secrets never stay secret for very long. Silas ended up going to Port Charles and struck up a romance with Sam McCall (Kelly Monaco). Detective Nathan West (Ryan Paevey), who believed he was Nina's brother, came to town to investigate Silas for Nina's murder. Ultimately, it was revealed that Nina was not actually dead, but was still very much in a coma (via Soap Central).
Eventually, Nina woke up and found her way back to Port Charles, just in time to interrupt Silas and Sam's blossoming love affair.
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