It might be a movie within last 10 years possibly watched on LifeTime.
Only thing I remember clearly is the end. The wife walks out of the police station and her partner in crime is waiting outside in the car and they drive away together?
I think it’s one of the woman’s husband that is killed. And the women act like they are helping with the investigation but no so much.
Sounds like the ending to Employee of the Month
http://www.imdb.com/title/tt0362590/?ref_=nv_sr_2