IMO, the SDSO investigators would have confirmed Dina's presence at the hospital. That is Investigation 101. Have you seen the case files? Do you know for a fact that no nurses, or any person in the ICU, were interviewed by LE?
The Sheriff has gone on record stating that the ONLY proof he has of Dina being at the hospital was her cell phone record pings. Anne Bremner has the records and according to Dina, Jonah has the records as well. As that Jonah stopped talking to Dina a year ago, I doubt she has any clue whom Jonah has shared those records with or why. I would imagine if Jonah suspects Dina had anything to do with Rebecca's death he is scared of her. The kids might be too.