Woman kills friend and detective solves murder finding an egg-shaped family relic

Okay, so I’m trying to find this movie based on the following information:
At the beginning, the woman who kills her friend confesses to have murdered her friend but they didn’t believe her because they thought she was covering the killer.
Before the real murderer was found, a neighbour of the victim was suspect because he used to climb to the roof to spy on them
The victim was arguinng with her friend and she tells her a lie: that she had sold a family relic (the egg), hence why her friend murdered her.
The next day, she moved her body and saw that she was laying on the egg. Then the detective sees the body and finds a bruise on the victim’s back.
Afterwards, the grandmother of the killer gives the detective an egg as a gift and he deduces that was what caused the bruise, solving the case.