[TOMT] tv show / movie Murder Mystery (fictional)

I remember the ending where the main person tells the murderer how they discovered she committed the murder of the man.
The main character leaves the woman inside the house, she gets a bottle of pills and a tub of chocolate ice cream, she takes it out back where there is a underground pool, she sits in a outdoor beach lounge chair and is seen eating a spoonful and crying a tear.
Implying that she regrets the murder or regrets someone knowing what she had done and is now committing suicide.
I believe it was a tv show or movie from and set in the 70’s – 80’s in California.
Ive already looked into Columbo or Murder She Wrote, found nothing, but it had that vibe.

[TOMT] tv show / movie Murder Mystery (fictional)