Plot hole: The suitcase with all the money is at the fake doctor guy. This makes absolutely no sense - it was given to the girl. Why would she hand it over to that guy when they could have done the splitting of the money right that night?
Plot hole: The happy ending twist, with Denzel getting the life insurance policy payout, couldn't happen. No insurance policy ever written would pay out if the policyholder's death resulted from participation in a crime.
Plot hole: She made Matt a real 1 Million dollar life insurance beneficiary to get 400,000 dollars. How did she know Matt would give her the money? If she was gonna murder her husband anyway, instead of doing this long elaborate plan on Matt, why not just kill her husband and collect his insurance policy?