Question: Is Nola really pregnant? She's taking medicine and the police say nothing about a pregnancy to Chris, when they show him Nola's diary.
Answer: Yes, she was pregnant. At the end, Mrs. Eastby's ghost confronts Chris about killing his unborn child by murdering Nola. This was intended as a literary plot device known as "exposition." It tells the audience that Nola was pregnant and that Chris, by his response, knew it was true, making his crime even more heinous.
Mrs. Eastby's ghost could just as easily be conjured up by Chris's own mind, which means that "she" wouldn't know anything that Chris wouldn't know. If you're going to be snarky, it helps to have thought through the possibilities a bit better.
Question: What's the story with Chris's accent? It certainly doesn't sound Irish.
Answer: No, she's not pregnant.
Wasn't there a clip of her with a positive pregnancy test? But in saying that, surely she would have written about it in her diary, and it would have shown up on her autopsy.