This answer contains spoilers… (view spoiler)[Yes, I think the author infers that the police kept investigating. With the mention of the newspaper article about a "murder/suicide," it is clear that Diana's death was definitively eventually classified as a murder, rather than suicide. And one can infer that when Nettie killed herself, even though she did not get time to write out the suicide note she had planned to write to confess to Diana's murder, probably because of her using the second bottle of the same poison that Nettie left by Diana's body, the police would have identified her as the killer. Surely, the police could investigate the purchase of that poison, despite Lucy encrypting the email address, and would have identified Nettie as the killer in that fashion. The author chose not to write all of this out for her own purposes, I guess. I too think it would have helped the end of the book to have fleshed this all out a bit more fully. (hide spoiler)]
Laurie There’s no Judy in this book. Do you mean Lucy? The police kept investigating, found the across the street neighbor who saw Ollie at Diana’s house the day she was killed. Then the police investigated Netties death. They were still investigating.