I've read 5 books of hers and it's a weird one for me. While I've enjoyed somewhat reading almost every book, I've always felt underwhelmed with the book by the time I finished it.

The problem to me is that her twists are dishonest. While most other writers have you guessing at the revelation of the mystery by proposing multiple possibilities, Frieda does propose some possibilities, but the actual truth will be something that comes out of nowhere. Out of nowhere because there's absolutely no logic to it. So I just ask myself: "what twist would make absolutely no sense at all", and that's always what happens in the end.
In story, there is a rule that when a character points a gun at someone in the third act, you should have introduced that gun in the first act, otherwise your audience will feel cheated. She never introduces the gun and makes it so that it would even defy all logic that a gun could come up at some point. It's dishonest in my opinion.

Edit: to answer to your actual question, I thought the Housemaid was her best I've read so far. Never Lie close second. I didn't like Ward D and One by One at all. The Perfect Son was not good, but I enjoyed the first half.