You must not read the Stephanie Plum mysteries by Janet Evanovich. She's had a triangle with Stephanie, Ranger, and Joe going on for 22 novels with no signs of stopping!
These cozy mystery movies are exactly like my cozy mystery novels. You know what you're getting with each one, except who did it. And I'm fine with that! Usually with the first in the series, the plucky female finds the body and/or is accused of the murder. More often than not, she is single and will start dating the detective. That was she can "help" with the investigations in future novels. HMM was promoting a new movie series Gourmet Detective which seems to follow that pattern, but with the roles reversed. She's the detective and he's a suspect in the murder. And I'll be watching!