Alissa Johnson's "Tempting Fate"

I loved Alissa Johnson's "Nearly a Lady" and so was prepared to enjoy this book as well. But I didn't, for several reasons.
Couples who grow up together in the same house almost as brother and sister *never* become lovers in real life, but for some reason authors, ever since Wuthering Heights, think that this is just a wonderful romance trope. Sorry, I can't buy into it.
The main couple here are 25 and 30 years old, but they behave like pre-teens (constantly bickering, literally grabbing each other's toys). The scene where Whit grabs Mirabelle's shopping box and then blackmails her into spying on his sister by holding it out of her reach is just cringe-inducing. No 30 year-old man who is the responsible head of his family behaves like that, even if he was doing that when he was 12 years old.
Finally, I cannot believe that a 25 year-old woman and a 30 year-old man would not recognize lust and/or romantic feelings for one another - the author would have the reader believe that Mirabelle has no clue as to what is going on with her feelings, and that is just not humanly possible at that age in a person of normal intelligence. If she were 12 years old, maybe, but not when she's an adult.